Catheter-based system for delivery and retrieval of a leadless pacemaker

ABSTRACT

Catheter-based delivery systems for delivery and retrieval of a leadless pacemaker include features to facilitate improved manipulation of the catheter and improved capture and docking functionality of leadless pacemakers. Such functionality includes mechanisms directed to deflecting and locking a deflectable catheter, maintaining tension on a retrieval feature, protection from anti-rotation, and improved docking cap and drive gear assemblies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application Ser. No. 62/408,494, filed Oct. 14, 2016, entitled,“EXPANDABLE SLEEVE FOR DELIVERY/RETRIEVAL OF A LEADLESS PACEMAKER”, U.S.Provisional Patent Application Ser. No. 62/434,537, filed Dec. 15, 2016,entitled, “EXPANDABLE SLEEVE FOR DELIVERY/RETRIEVAL OF A LEADLESSPACEMAKER,” and U.S. Provisional Patent Application Ser. No. 62/503,888,filed May 9, 2017, entitled “CATHETER-BASED DELIVERY SYSTEM FORDELIVERING A LEADLESS PACEMAKER EMPLOYING A LOCKING HUB”. Thedisclosures of these co-pending related applications are incorporated byreference in their entirety into this present application.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

FIELD

The present disclosure relates to leadless cardiac pacemakers andrelated delivery and retrieval systems and methods. More specifically,the present disclosure relates to devices and methods for delivering andretrieving a leadless cardiac pacemaker via a catheter-based deliverysystem.

BACKGROUND

Cardiac pacing by an artificial pacemaker provides an electricalstimulation of the heart when its own natural pacemaker and/orconduction system fails to provide synchronized atrial and ventricularcontractions at rates and intervals sufficient for a patient's health.Such antibradycardial pacing provides relief from symptoms and even lifesupport for hundreds of thousands of patients. Cardiac pacing may alsoprovide electrical overdrive stimulation to suppress or converttachyarrhythmias, again supplying relief from symptoms and preventing orterminating arrhythmias that could lead to sudden cardiac death.

Cardiac pacing by currently available or conventional pacemakers isusually performed by a pulse generator implanted subcutaneously orsub-muscularly in or near a patient's pectoral region. Pulse generatorparameters are usually interrogated and modified by a programming deviceoutside the body, via a loosely-coupled transformer with one inductancewithin the body and another outside, or via electromagnetic radiationwith one antenna within the body and another outside. The generatorusually connects to the proximal end of one or more implanted leads, thedistal end of which contains one or more electrodes for positioningadjacent to the inside or outside wall of a cardiac chamber. The leadshave an insulated electrical conductor or conductors for connecting thepulse generator to electrodes in the heart. Such electrode leadstypically have lengths of 50 to 70 centimeters.

Although more than one hundred thousand conventional cardiac pacingsystems are implanted annually, various well-known difficulties exist,of which a few will be cited. For example, a pulse generator, whenlocated subcutaneously, presents a bulge in the skin that patients canfind unsightly, unpleasant, or irritating, and which patients cansubconsciously or obsessively manipulate or “twiddle”. Even withoutpersistent manipulation, subcutaneous pulse generators can exhibiterosion, extrusion, infection, and disconnection, insulation damage, orconductor breakage at the wire leads. Although sub-muscular or abdominalplacement can address some concerns, such placement involves a moredifficult surgical procedure for implantation and adjustment, which canprolong patient recovery.

A conventional pulse generator, whether pectoral or abdominal, has aninterface for connection to and disconnection from the electrode leadsthat carry signals to and from the heart. Usually at least one maleconnector molding has at least one terminal pin at the proximal end ofthe electrode lead. The male connector mates with a corresponding femaleconnector molding and terminal block within the connector molding at thepulse generator. Usually a setscrew is threaded in at least one terminalblock per electrode lead to secure the connection electrically andmechanically. One or more O-rings usually are also supplied to helpmaintain electrical isolation between the connector moldings. A setscrewcap or slotted cover is typically included to provide electricalinsulation of the setscrew. This briefly described complex connectionbetween connectors and leads provides multiple opportunities formalfunction.

Other problematic aspects of conventional pacemakers relate to theseparately implanted pulse generator and the pacing leads. By way ofanother example, the pacing leads, in particular, can become a site ofinfection and morbidity. Many of the issues associated with conventionalpacemakers are resolved by the development of a self-contained andself-sustainable pacemaker, or so-called leadless pacemaker, asdescribed in the applications cited below.

Similar to active fixation implantable leads used with conventionalpulse generators, leadless pacemakers are typically fixed to anintracardial implant site by an actively engaging mechanism such as ascrew or helical member that screws into the myocardium.

Leadless pacemakers are typically delivered to an intracardial implantsite via a delivery system including catheters, sheaths and/orintroducers. Introduction of a leadless pacemaker into the venous systemand navigation of the leadless pacemaker through and past delicatetissues and anatomical structures to the implantation site is acomplicated task. To achieve this task, manipulation of the sheaths,catheters and introducers relative to each other must often be precise.

Similarly, retrieval of previously implanted leadless pacemakersrequires precise manipulation of the catheters, sheaths and/orintroducers to secure the implanted leadless pacemaker, disengage theleadless pacemaker from the intracardial implant site, and extract theleadless pacemaker through the venous system. Absent sufficient controland precision during the retrieval process, damage to one or more of theleadless pacemaker, the cardiac tissue of the implant site, and thevenous system may result.

There is a need in the art for systems and methods that facilitateprecise manipulation of a leadless pacemaker delivery and systems forpurposes of both implanting and removing leadless pacemakers fromintractardial implant sites.

SUMMARY OF THE DISCLOSURE

In one embodiment of the present disclosure a handle for a catheter isprovided. The catheter includes a deflectable catheter section and apull wire coupled to the deflectable catheter section and definesdefining a longitudinal axis. The handle includes a housing, a hubdisposed within the housing and coupled to the pull wire, and adeflection lever coupled to the hub. The deflection lever extends from afirst side of the housing and is movable between a first lever positionin which the deflection lever extends away from the longitudinal axis ata first angle and a second lever position in which the deflection leverextends away from the longitudinal axis at a second angle less than thefirst angle. The handle further includes a brake assembly coupled to thehub and rotatable between a first brake position in which the brakeassembly applies a first resistance to rotation of the hub and a secondbrake position in which the brake assembly applies a second resistanceto rotation of the hub greater than the first resistance. Movement ofthe lever from the first lever position to the second lever positionrotates the hub, pulling the pull wire to deflect the deflectablecatheter section.

In certain implementations, the lever extends from the housing at leastpartially in a proximal direction and may further define a moment armhaving a predetermined length relative to the center of the hub. Thefirst and second angles of the lever may also be within predeterminedranges.

The hub may also include a wall extending at least partially around thehub that at least partially guides the pull wire. The wall may bedisposed at a predetermined radius from a center of the hub and have apredetermined arc length. A multiplier post about which the pull wire isrouted may also be included. The multiplier post may generally beadapted to remain in a fixed position relative to the housing when thehub is rotated.

The brake assembly may include a lever extending from the housingopposite the deflection lever. For example, when in the first brakeposition, the lever may extend at least partially in a proximaldirection such that rotation of the brake assembly from the first brakeposition to the second brake position may include rotating the brakeassembly in a distal direction.

In certain implementations, movement of the deflection lever from thefirst lever position to the second lever position causes rotation of thehub in a first rotation direction and the brake assembly is rotatablebetween the first brake position and the second brake position byrotating the brake assembly in the first direction.

In another embodiment of the present disclosure, a handle for a catheteris provided. The catheter includes a deflectable catheter section and apull wire coupled to the deflectable catheter section. The handledefines a longitudinal axis and includes a housing, a hub disposedwithin the housing and coupled to the pull wire, and a deflection levercoupled to the hub. The deflection lever extends from a first side ofthe housing and is movable between a first lever position and a secondlever position to deflect the deflectable catheter section. The handlefurther includes a brake assembly including a knob coupled to the huband rotatable between a first brake position in which the brake assemblyapplies a first resistance to rotation of the hub and a second brakeposition in which the brake assembly applies a second resistance torotation of the hub that is greater than the first resistance. The brakeassembly further includes a brake lever coupled to the knob andextending from a second side of the housing opposite the first side.

In certain implementations, the brake assembly further includes a hubwasher disposed within the housing and rotationally fixed relative tothe hub such that the first resistance and the second resistance torotation of the hub results from compression of the hub washer againstthe housing.

The brake assembly may further include a threaded shaft coupled to theknob and extending through the hub washer such that rotation of the knobcauses translation of the knob along the shaft and compression of thehousing between the knob and the hub washer. In such implementations,the knob may be coupled to the threaded shaft by a threaded insertdisposed within the knob. The brake assembly may further include a brakewasher disposed between the knob and the housing. In implementationsincluding the threaded shaft, the threaded shaft may include a shaft endthat is rotationally fixed within the housing.

In certain implementations the knob is rotatable from the first brakeposition to the second brake position by rotating the brake lever in afirst direction and movement of the lever between the first leverposition and the second lever position causes the hub to rotate in thefirst direction.

In yet another embodiment disclosed herein, a system for at least one ofdelivery or retrieval of an implantable medical device is provided. Thesystem includes a deflectable catheter section, a pull wire coupled tothe deflectable catheter section, and a handle defining a longitudinalaxis. The handle further includes a housing, a hub disposed within thehousing and coupled to the pull wire, and a deflection lever coupled tothe hub. The deflection lever extends from a first side of the housingand is movable between a first lever position and a second leverposition to deflect the deflectable catheter section. The handle furtherincludes a brake assembly coupled to the hub and rotatable between afirst brake position in which the brake assembly applies a firstresistance to rotation of the hub and a second brake position in whichthe brake assembly applies a second resistance to rotation of the hubgreater than the first resistance.

In certain implementations, the deflection lever extends from a firstside of the housing and the brake assembly includes a brake leverextending from a second side of the housing opposite the first housing.In such implementations, the deflection lever substantially may extendin one of a proximal and a distal direction and the brake assembly maymovable between the first brake position and the second brake positionby applying a force to a brake lever in the distal and proximaldirection, respectively.

In certain implementations, the deflectable catheter may passivelyreturn to an undeflected state and the brake assembly may be rotatableinto a third brake position in which sufficient resistance is providedto prevent passive return of the deflectable catheter.

In still another embodiment, a handle of a catheter system is provided.The catheter system includes a sheath and a retrieval feature disposedwithin the sheath. The handle includes a first handle portion includinga pawl and a second handle portion including a rack surface extendinglongitudinally along at least a section of the second handle portion.The rack surface is shaped to engage the pawl and is disposed, at leastpartially, within the first handle portion. The second handle portion iscoupled to the retrieval feature such that the retrieval feature may beretracted by displacing the second handle portion relative to the firsthandle portion. The second handle portion is movable in a proximaldirection from a first position in which the pawl does not engage therack surface to a second position in which the pawl engages the racksurface.

In certain implementations, the first handle portion may further includea second pawl disposed opposite the pawl.

When in the second position, the rack surface and the pawl may preventmovement of the second handle portion in a distal direction.

In some implementations, the pawl includes a release that, whenactuated, causes the pawl to disengage from the rack surface. The pawlmay be is supported by a pivot pin and the release may be a push buttonthat, when depressed, causes the pawl to rotate about the pin and todisengage the rack surface. The pawl may also be biased towardsengagement with the rack surface by a biasing element. The biasingelement may be, for example, at least one of a coil spring or a linearspring coupled to the pawl.

The rack surface may extends about the second handle portion such that,when in the second position, the second handle portion is rotatablerelative to the first handle portion without disengaging the pawl fromthe rack surface. The second handle portion may define a retentionfeature disposed proximal the rack surface such that the pawl engagesthe retention feature when the second handle portion is disposed at adistal extent relative to the first handle portion.

In another embodiment, a retrieval system for retrieving an implantedmedical device is provided. The retrieval system includes a cathetershaft, a snare extending through the catheter shaft, and a handlecoupled to a proximal end of the catheter shaft. The handle furtherincludes a first handle portion and a second handle portion disposed atleast partially within the first handle portion. The second handleportion is coupled to the snare such that the snare may be retracted bydisplacing the second handle portion relative to the first handleportion. The handle further includes a ratchet selectively coupling thefirst handle portion and the second handle portion. The ratchet allowsproximal movement of the second handle portion relative to the firsthandle portion while resisting distal movement of the second handleportion relative to the first handle portion.

In some implementations, the first handle portion includes a pawl andthe second handle portion includes a rack, the ratchet formed by thepawl and the rack.

The first handle portion may include a release that, when actuated,reduces resistance to distal movement of the second handle portionrelative to the first handle portion. The release may, in certainimplementations, include at least one button disposed on an exteriorsurface of the first handle portion.

In some implementations the first handle portion is movable between afirst position in which the ratchet does not couple the first handleportion and the second handle portion and a second position in which theratchet couples the first handle portion and the second handle portion.

The second handle portion may also be rotatable within the first handleportion when the second handle portion is in the second position.

In yet another embodiment, a handle for a catheter system is provided.The catheter system is adapted to retrieve an implanted medical andincludes a sheath and a retrieval feature disposed within the sheath.The handle includes a first handle portion including a first lockingfeature and a second handle portion including a second locking feature.The second handle portion is coupled to the retrieval feature such thatthe retrieval feature may be withdrawn into the sheath by displacing thesecond handle portion relative to the first handle portion. The secondhandle portion is also movable from a first position in which the firstlocking feature does not engage the second locking feature to a secondposition in which the first locking feature engages the second lockingsurface.

In some implementations the first locking feature and the second lockingfeature restrict distal movement of the second handle portion after thesecond handle portion is moved into the second position.

The second handle portion may further include a third locking featuredisposed distal the second locking feature, the second handle portionfurther movable in a proximal direction into a third position in whichthe locking feature engages the third locking feature.

The first handle portion and the second handle portion may have a commonlongitudinal axis and the second handle portion may be movable relativeto the first handle portion along the common longitudinal axis.

In another implementation, the locking feature may include a releasemechanism that, when actuated, disengages the first locking feature fromthe second locking surface.

In one embodiment of the present disclosure, a handle of a cathetersystem is provided. The catheter system including a sheath and a snaredisposed within the sheath. The handle includes a first handle portionincluding a wall and a protrusion extending inwardly from the wall and asecond handle portion including a ratchet wheel disposed at a distal endof the second handle portion. The second handle portion is movable in aproximal direction from a first position in which the ratchet wheel isnot aligned with the protrusion and a second position in which theratchet wheel is aligned with the protrusion. When in the secondposition, the second handle portion is rotatable in a first directionbut rotation in a second direction opposite the first direction isobstructed by the protrusion. In certain implementations, the firstdirection is clock-wise and the second direction is counter-clockwise.

In one implementation, the ratchet wheel includes a pair of offsetsemi-circular lobes.

In another implementation, the protrusion includes a fin. In suchimplementations the fin may include multiple adjacent fin segmentsdefining gaps therebetween, the gaps being less than a width of theratchet wheel.

The handle may further include a locking feature that locks the secondhandle portion in the second position when the second handle portion ismoved into the second position. In such implementations, the firsthandle portion may include a pawl proximal the protrusion and the secondhandle portion includes a rack surface proximal the ratchet wheel, thelocking feature including the pawl and the rack surface.

In certain implementations, the handle may further include a releasethat, when actuated, releases the second handle portion such that thesecond handle portion may be moved from the second position to the firstposition. In such implementations, the first handle portion may includeat least one button and the release may include the at least one button.

In yet another embodiment a handle of a catheter system is provided. Thecatheter system includes a sheath and a snare disposed within thesheath. The handle includes a first handle portion including a pawl anda second handle portion disposed at least partially within the firsthandle portion. The second handle portion is coupled to the snare suchthat the snare may be retracted by displacing the second handle portionrelative to the first handle portion. The second handle portion includesa rack surface extending longitudinally along at least a section of thesecond handle portion, the rack surface including a pair of adjacentrack teeth, and a ratchet wheel disposed between the rack teeth of thepair of adjacent rack teeth. The second handle portion is movable in aproximal direction from a first position in which the pawl is disengagedfrom each of the linear rack and the ratchet wheel and a second positionin which the pawl is engaged with each of the linear rack and theratchet wheel.

In certain implementations, when in the second position, engagement ofthe pawl with the linear rack resists distal movement of the secondhandle portion. In such implementations, when in the second position,the second handle portion may be rotatable in a first direction butengagement of the pawl with the ratchet wheel may resist rotation of thesecond handle portion in a second direction opposite the firstdirection.

In some implementations, the ratchet wheel may include a plurality ofratchet wheel teeth disposed every sixty degrees about a perimeter ofthe ratchet wheel.

The handle may, in certain implementations, include a release that, whenactuated, disengages the pawl from each of the rack surface and theratchet wheel such that the second handle portion may be moved in adistal direction from the second position to the first position.

The rack surface may, in some implementations, include a second pair ofadjacent rack teeth and a second ratchet wheel disposed between the rackteeth of the second pair of adjacent rack teeth.

In still another implementation of the present disclosure, a retrievalsystem for retrieving an implanted medical device is provided. Theretrieval system includes a catheter shaft, a snare extending throughthe catheter shaft, and a handle coupled to a proximal end of thecatheter shaft. The handle includes a first handle portion including afirst counter-rotation feature and a second handle portion including asecond counter-rotation feature, the second handle portion coupled tothe snare such that the snare is retracted by displacing the secondhandle portion relative to the first handle portion. The second handleportion is movable from a first position in which the firstcounter-rotation feature does not engage the second counter-rotationfeature to a second position in which the first locking feature engagesthe second locking surface. In some implementations, when in the secondposition, the second handle portion may be restricted from movingtowards the first position.

In certain implementations, the first counter-rotation feature includesa protrusion extending from a wall of the first handle portion.

The second counter-rotation feature may, in some implementations,include a ratchet wheel disposed on a distal end of the second handleportion. In such implementations, the ratchet wheel may include a pairof offset semi-circular lobes.

The retrieval system may further include a release that, when actuated,reduces the restriction to movement of the second handle portion towardsthe first position.

In an embodiment of the present disclosure, a system for retrieving animplantable medical device from within a patient is provided. The systemincludes a torque shaft, a retrieval feature extending through thetorque shaft, and a handle coupled to the torque shaft such thatrotation of the handle rotates the torque shaft. The handle includes atorsion release assembly coupled to the retrieval feature that furtherincludes a first gear and that is rotationally supported within thehandle. The system further includes a shuttle coupled to the handle andincluding a second gear. The shuttle is translatable between a firstshuttle position in which the first gear is engaged with the second gearsuch that rotation of the handle rotates the torsion release assembly,and a second shuttle position in which the first gear is disengaged fromthe second gear such that rotation of the handle does not rotate thetorsion release assembly. The shuttle may be rotationally fixed relativeto the handle. In certain implementations, the first shuttle positioncorresponds to a proximal shuttle position and the second shuttleposition is a distal shuttle position. Further, when in the secondshuttle position, the first gear may be disposed within the second gear

In certain implementations, the system further includes a bearingdisposed within the housing such that the torsion release assembly isrotationally supported within the handle by the bearing. The bearing mayinclude a ball bearing including at least one of metal or plastic balls.

The first gear may have a substantially square cross-section and thesecond gear may define a substantially square cavity into which thefirst gear is inserted when the shuttle is in the first shuttleposition, in such implementations, the second gear may extend along alongitudinal axis normal to a cross-sectional plane of the second gearand the second gear may include a proximal gear end. The proximal gearend may include a first half having a first face defining a first planeoriented at a first angle relative to the cross-sectional plane and asecond half having a second face defining a second plane oriented at asecond angle relative to the cross-sectional plane such that the firstangle and the second angle are supplementary and the first plane and thesecond plane intersect along a line perpendicular to the longitudinalaxis.

In certain implementations, the first gear may include a shaft and aplurality of first splines extending along the shaft. The second gearmay include at least one second spline extending parallel to each of theplurality of first splines such that, when in the second position, theat least one second spline is disposed between adjacent splines of theplurality of first splines.

In another embodiment, a torsion release system for an elongated body ofa medical device having a rotatable handle is provided. The torsionrelease system includes a first gear coupled to the elongated body androtationally supported within the rotatable handle and a second gearrotationally fixed to the rotatable handle. The first gear and thesecond gear transition between a first configuration in which the firstgear is engaged with the second gear such that rotation of the rotatablehandle rotates the first gear and transmits torque to the elongatedbody, and a second configuration in which the first gear is disengagedfrom the second gear such that rotation of the handle does not rotatethe first gear. In certain implementations, transition between the firstconfiguration and the second configuration includes translating thesecond gear between a first position corresponding to the firstconfiguration and a second position corresponding to the secondconfiguration.

When in the second configuration, the first gear may freely rotatablewithin the housing. For example, in some implementations, the first gearmay be rotationally supported within the rotatable handle by a ballbearing.

When in the second configuration, the first gear may be at leastpartially disposed within the second gear. In such implementations, thefirst gear may include has a substantially square cross-section and thesecond gear may define a substantially square cavity into which thefirst gear is inserted in the second configuration.

In yet another embodiment, a system for retrieving an implantablemedical device from within a patient is provided. The system includes atorque shaft, a retrieval feature extending through the torque shaft, ahandle coupled to the torque shaft such that rotation of the handlerotates the torque shaft, a selectively rotatable body coupled to theretrieval feature, and a shuttle rotationally fixed relative to thehandle. The shuttle and selectively rotatable body transition between afirst configuration in which the shuttle is engaged with the selectivelyrotatable body, thereby preventing rotation of the selectively rotatablebody relative to the handle, and a second configuration in which theshuttle is disengaged from the selectively rotatable body and theselectively rotatable body is permitted to rotate relative to thehandle.

In some implementations, the selectively rotatable body includes a firstgear and the shuttle includes a second gear, the first gear engaging thesecond gear when in the first configuration.

In certain implementations, when the retrieval feature is under torsionin a first rotational direction and the system is in the firstconfiguration, transition into the second configuration may release thetorsion and causes rotation of the retrieval feature and the selectivelyrotatable body in a second rotational direction opposite the firstdirection.

The system may further include a rotatable mount disposed within thehandle. In such implementations, the selectively rotatable body may besupported by the rotatable mount within the handle.

In one embodiment of the present disclosure, a system for retrieving animplantable medical device from within a patient is provided. The systemincludes a catheter shaft, a handle coupled to a proximal end of thecatheter shaft, and a docking cap coupled to a distal end of thecatheter shaft. The docking cap defines a docking cap volume andincludes a proximal cap end coupled to the catheter shaft, a distalannulus disposed opposite the proximal cap, and a plurality oflongitudinal members extending between the distal annulus and theproximal cap end, such that adjacent pairs of the plurality oflongitudinal members define openings into the docking cap volume.

In certain implementations, the system includes a sheath disposed overat least a portion of the openings. In such implementations, the sheathmay be or include a fluorinated ethylene propylene (FEP) sheet. Also insuch implementations, the sheath may be shrink-wrapped about thelongitudinal members.

In some implementations, the distal annulus includes a distal face, aninternal surface perpendicular to the distal face, and a curvedtransition between the distal face and the internal surface. The curvedtransition may have a radius of curvature and an arc length within apredetermined range.

The system may further include a torque feature disposed on an interiorsurface of at least one of the longitudinal members. The torque featuremay be shaped to engage a portion of the implantable medical deviceduring retrieval. For example, the torque may include a protrusionextending into the docking cap volume. In some implementations, thetorque feature may be offset from the distal annulus,

The docking cap may be formed from various materials including, withoutlimitation, one or more of stainless steel (such as 304 stainlesssteel), titanium, and a polymer, such as polyether ether ketone (PEEK).In certain implementations, the material may also be loaded with aradiopaque additive,

In another embodiment, a catheter is provided. The catheter includes acatheter shaft having a distal shaft end and a docking cap coupled tothe distal shaft end. The docking cap includes a proximal cap endcoupled to the distal shaft end, a distal annulus disposed opposite theproximal cap, and a plurality of longitudinal members extending betweenthe distal annulus and the proximal cap end such that adjacent pairs ofthe plurality of longitudinal members define openings into the dockingcap volume.

In certain implementations, the catheter includes a sheath disposed overat least a portion of the openings. In such implementations, the sheathmay be or include a fluorinated ethylene propylene (FEP) sheet that maybe shrink-wrapped about the longitudinal members.

In some implementations, the distal annulus includes a distal face, aninternal surface perpendicular to the distal face, and a curvedtransition between the distal face and the internal surface. The curvedtransition may have a radius of curvature and an arc length within apredetermined range.

The catheter may further include a torque feature disposed on aninterior surface of at least one of the longitudinal members. The torquefeature may be shaped to engage a portion of the implantable medicaldevice during retrieval. For example, the torque may include aprotrusion extending into the docking cap volume. In someimplementations, the torque feature may be offset from the distalannulus.

In another embodiment of the present disclosure, a system for retrievingan implantable medical device from within a patient is provided. Thesystem includes a catheter shaft, a torque shaft disposed within thecatheter shaft, and a handle including a first handle portion coupled tothe catheter shaft and a second handle portion coupled to the torqueshaft. The system further includes a drive gear coupled to a distal endof the torque shaft and including a drive gear torque feature, the drivegear rotatable by rotating the torque shaft, and a docking cap rotatablycoupled to a distal end of the catheter shaft. The docking cap defines arecess for at least partially receiving the drive gear and includes arecess torque feature disposed within the recess. When received by thedocking cap, the drive gear is rotatable in a first direction into anengaged position in which the drive gear torque feature engages therecess torque feature such that further rotation of the drive gearrotates the docking cap in the first direction. In certainimplementations, rotation of the drive gear in a second directionopposite the first direction when in the engaged position may disengagethe drive gear torque feature from the recess torque feature.

In certain implementations, the drive gear includes a distal portionincluding a cuboid body having a substantially square shape. The cuboidbody may include distal rounded corners. In some implementations, thesquare distal face may define a diagonal between a pair of opposingcorners of the square distal face and the recess may be defined by apair of first opposing walls and a pair of second opposing walls, thefirst opposing walls being longer than the diagonal and the secondopposing walls being shorter than the diagonal. In such implementations,the recess torque feature is one or both of the first opposing walls andthe drive gear torque feature is one or both of the opposing corners ofthe square distal face.

The docking cap may define a cutout in one of the first opposing walls.In such implementations, the cutout is shaped to receive one of theopposing corners of the drive gear when the drive gear is in the engagedposition.

The drive gear may, in certain implementations, include a proximalportion that including a proximally tapering body.

The docking cap may include a protrusion extending laterally into therecess, the recess torque feature being the protrusion. In suchimplementations, the drive gear includes an outer face including aconcave portion shaped to receive the protrusion during rotation of thedrive gear in the first direction, a substantially flat portion, and atransition portion coupling the concave portion to the substantiallyflat portion such that the drive gear torque feature is the transitionportion.

The docking cap may include a proximally slanted surface extending intothe recess. In such implementations, the proximally slanted surface isshaped to guide the drive gear into the engaged position in response torotation of the drive gear in the first direction.

In another embodiment, a system for retrieving an implantable medicaldevice from within a patient is provided. The system includes a drivegear and a docking cap shaped to receive a proximal end of theimplantable medical device. The drive gear is at least partiallyretractable within the docking cap and, when at least partiallyretracted within the docking cap, rotation of the drive gear in a firstdirection causes interference between the drive gear and the docking capsuch that further rotation of the drive gear in the first directionrotates each of the drive gear and the docking cap. In someimplementations, the drive gear interferes with the docking cap at aplurality of locations.

In some implementations, the drive gear includes a rounded distal cornerand the docking cap includes an internal wall partially defining arecess within the docking cap such that the interference is between therounded distal corner and the internal wall.

The docking cap may define a recess and include a protrusion extendinglaterally into the recess. In such implementations, the drive gearincludes an outer face including a concave portion shaped to receive theprotrusion during rotation of the drive gear in the first direction, asubstantially flat portion, and a transition portion coupling theconcave portion to the substantially flat portion. In such cases, theinterference occurs between the transition portion and the protrusion.

In some implementations, the drive gear includes a distal portionincluding a cuboid body having a substantially square distal face anddistal rounded corners. The drive gear may also include a proximalportion including a proximally tapering body.

In yet another embodiment, a system for delivering and retrieving animplantable medical device from within a patient is provided. The systemincludes a catheter shaft, a torque shaft disposed within the cathetershaft, and a handle including a first handle portion coupled to thecatheter shaft and a second handle portion coupled to the torque shaft.The system further includes a drive gear coupled to a distal end of thetorque shaft, the drive gear including a distal portion including acuboid body having a substantially square distal face and rounded distalcorners, and a docking cap rotatably coupled to a distal end of thecatheter shaft. The square distal face of the drive gear defines adiagonal between opposing corners of the square distal face. Theincludes a pair of first opposing internal walls that are each longerthan the diagonal, and a pair of second opposing internal walls that areeach shorter than the diagonal. The pair of first internal opposingwalls and the pair of second opposing internal walls define a recess forat least partially receiving the drive gear.

In some implementations, when received within the recess, the drive gearis rotatable in a first direction to engage at least one of the opposingcorners with a respective one of the pair of first opposing internalwalls such that, once engaged, rotation of the drive gear rotates thedocking cap. In such implementations, when the at least one of theopposing corners is engaged with the respective one of the pair of firstopposing internal walls, rotation of the drive gear in a seconddirection opposite the first direction may disengage the at least one ofthe opposing corners from the respective one of the pair of firstopposing internal walls.

The drive gear may, in certain implementations, include a proximalportion coupled to the distal portion including a proximally taperingbody.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe claims that follow. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIGS. 1A and 1B are, respectively, side and end views of an exampleleadless cardiac pacemaker.

FIG. 1C is a diagrammatic medial-lateral cross section of a patientheart illustrating example implantation of leadless pacemakers in thepatient heart.

FIG. 1D is one embodiment of a system for delivering and/or retrieving aleadless pacemaker.

FIGS. 2A-2B are close-up views of a distal portion of the system.

FIGS. 3A-3B are schematic side and cross-sectional views of a pacemakersheath.

FIGS. 4A-4G are side views of a delivery system approaching, and thenattaching to, a pacemaker.

FIGS. 5A-5C show various close-up views of a distal portion of aretrieval catheter system employing alternative capture mechanisms.

FIGS. 6-7 are various views of one embodiment of a pacemaker having aretrieval feature.

FIGS. 8A-8B are various views of another embodiment of a pacemakerhaving a retrieval feature.

FIGS. 9A-9B are plan views of a handle for use with a retrieval and/ordelivery system in an extended and depressed configuration,respectively.

FIGS. 10A-10B are isometric bottom views of the handle of FIGS. 9A-9B,respectively, with a housing portion removed.

FIG. 10C is a bottom view of the handle of FIG. 9B with a housingportion removed.

FIGS. 11A-11B are plan views of the handle of FIG. 9B with a brakeassembly in a first and second position, respectively.

FIG. 12 is a cross-sectional side view of the brake assembly of FIGS.11A 11B.

FIGS. 13A-13C are cross-sectional side view of a handle of a retrievalsystem including a first implementation of a tensioning assembly.

FIGS. 14A-14B are cross-sectional side views of alternative handles of aretrieval system including an alternative implementation of a tensioningassembly.

FIG. 15A is a plan view of a spring for use in the tensioning assembliesof FIGS. 14A-14B.

FIG. 15B is an isometric view of a spring for use in the tensioningassemblies of FIGS. 14A-14B.

FIG. 15C is a side elevation view of a spring for use in the tensioningassemblies of FIGS. 14A-14B.

FIG. 16A is a cross-sectional side view of a handle of a retrievalsystem including an anti-rotation assembly.

FIG. 16B-16C are isometric detail views of the anti-rotation assembly ofFIG. 16A.

FIG. 17A-17B are detail views of protrusions that may be incorporatedinto the anti-rotation assembly of FIG. 16A.

FIG. 18A is an isometric view of a proximal handle portion shaft for usein a handle of a retrieval system including anti-rotation features.

FIG. 18B is a cross-sectional view of a handle including the shaft ofFIG. 18A.

FIGS. 19A-19B are cross-sectional side views of a handle including atorsion relief mechanism in an engaged and disengaged configurationrespectively.

FIG. 20A is an isometric view of a shuttle assembly for use in thehandle of FIGS. 19A-19B.

FIG. 20B is an isometric view of a torsion release assembly of thehandle of FIGS. 19A-19B.

FIGS. 20C-20D are side views of the shuttle assembly of FIG. 20A and thetorsion release assembly of FIG. 20B in disengaged and engagedconfigurations, respectively.

FIG. 20E is a side detail view of a proximal portion of the shuttleassembly of FIG. 20A.

FIGS. 20F-20H are isometric views of the shuttle assembly of FIG. 20Aand the torsion release assembly of FIG. 20B illustrating engagement ofthe shuttle assembly and the torsion release assembly.

FIG. 21 is an isometric view of an alternative handle including atorsion relief mechanism.

FIGS. 22A-22B are top views of a distal end of a catheter retrievalsystem during capture and docking of a leadless pacemaker.

FIGS. 22C-22D are isometric views of a docking cap for use with aretrieval system.

FIG. 22E is an end view in a proximal direction of the docking cap ofFIGS. 22C-22D.

FIGS. 22F-22G are a side view and a side cross-sectional view of thedocking cap of FIGS. 22C-22D.

FIG. 22H is a side cross-sectional detail view of the docking cap ofFIGS. 22C-22D.

FIGS. 23A-23C are isometric views of a docking system at differentstages of a docking operation.

FIG. 23D-23E are end views in a proximal direction of the docking systemillustrating a drive gear in a disengaged and engaged configuration witha docking cap, respectively.

FIG. 24 is an isometric view of the drive gear of FIGS. 23A-23E.

FIG. 25 is an isometric view of the docking cap of FIGS. 23A-23E.

FIG. 26 is an end view in a proximal direction of an alternative dockingsystem.

FIG. 27 is an isometric view of a second alternative docking system.

FIG. 28 is an isometric view of a drive gear of the second alternativedocking system of FIG. 27.

FIG. 29 is an isometric view of a docking cap of the second alternativedocking system of FIG. 27.

FIG. 30A is an isometric view of a third alternative docking system.

FIG. 30B is an isometric cross-sectional view of a docking cap of thethird alternative docking system of FIG. 30.

FIG. 31 is an embodiment of a delivery system for delivering a leadlesspacemaker.

FIG. 32A is a close-up view of a distal portion of the delivery systemwith an atraumatic end of the delivery system proximal of the leadlesspacemaker.

FIG. 32B is a diagrammatic longitudinal cross section of the leadlesspacemaker and delivery system in the condition illustrated in FIG. 32A.

FIG. 32C is the same view as FIG. 32A, except the atraumatic end of thedelivery system has been distally displaced over the leadless pacemaker.

FIG. 32D is a diagrammatic longitudinal cross section of the leadlesspacemaker and delivery system in the condition illustrated in FIG. 32C.

FIGS. 33A-35B are schematic side and cross-sectional views of a sleeve.

FIG. 36A-36B are radiopaque markers in accordance with certainembodiments.

FIG. 37-40 are flow charts outlining methods of manufacturing the sleeveand its joining to a tubular body of the catheter sheath to become partof the catheter sheath.

FIG. 41 is an isometric view of an alternative sleeve.

FIGS. 42A is a side elevation view of the alternative sleeve of FIG. 41.

FIGS. 42B-42D are transverse cross-sectional views of the alternativesleeve of FIG. 41.

DETAILED DESCRIPTION

The present disclosure is directed to a delivery and retrieval systemsand associated methodology for delivering and retrieving leadlesspacemakers to and from an implantation site in a patient.

As discussed below, in one embodiment, a delivery and retrieval systemis provided including a deflectable catheter. To cause deflection of thecatheter, a lever is included in a handle of the delivery and retrievalsystem. The lever is coupled to a hub that is in turn coupled to adeflectable tip of the deflectable catheter by a pull wire. During use,the lever is depressed to cause rotation of the hub, which pulls thepull wire and deflects the deflectable tip. In certain implementations,the lever is adapted for use with a single hand, thereby enabling aphysician to perform additional tasks with his or her other hand. Thedelivery and retrieval system may further include a brake that ismovable along a range of positions to increase resistance to rotation ofthe hub. Accordingly, a physician may depress the lever and apply thebrake to reduce or eliminate the need for the physician to maintainforce on the lever to maintain deflection of the catheter.

In another embodiment, a retrieval system having a tensioning system isprovided. The tensioning assembly is incorporated into a handle of theretrieval system and includes a ratcheting mechanism that enables a userto apply and maintain tension on a snare or similar retrieval mechanism.The ratchet assembly generally couples a proximal handle portion and adistal handle portion of the retrieval system such that when the ratchetmechanism is engaged, the proximal handle portion may be movedproximally relative to the distal handle portion to increase tension butis prevented from translating in a distal direction absent actuation ofa release mechanism.

In yet another embodiment, an anti-rotation assembly for a retrievalsystem is provided. The anti-rotation system resists or preventsrotation of a proximal handle portion of the retrieval system followingcapture and docking of a leadless pacemaker or similar implantablemedical device. The anti-rotation functionality is achieved by a ratchetwheel disposed at the end of a shaft of the proximal handle portion. Theratchet wheel is positioned such that as the proximal handle portion ismoved proximally relative to a distal handle portion, the ratchet wheelaligns with protrusions extending inwardly into the distal handleportion. The ratchet wheel and protrusions interact such that rotationin a first direction (generally corresponding to unscrewing of aleadless pacemaker or similar implantable medical device) is permittedwhile rotation in an opposite direction is obstructed.

In still another embodiment, a torsion release system for a handle of aretrieval system is provided. The system is generally adapted to enabledissipation of tension applied to a snare or similar retrieval mechanismduring capture and docking of a leadless pacemaker or similarimplantable medical device. The system includes a first gear that isrotatable mounted within a handle and coupled to the retrievalmechanism. A shuttle is rotationally fixed but translatable relative tothe handle such that when in a first position, a second gear coupled tothe shuttle engages the first gear and rotation of the handle results inrotation of retrieval mechanism. In a second position, the shuttle isdisengaged from the first gear, allowing the first gear to spin freelywithin a rotatable mount and enabling dissipation of torsion built upwithin the retrieval mechanism.

In yet another embodiment, an improved docking cap for a retrievalsystem is provided. The improved docking cap includes various featuresto improve capture and docking of leadless pacemakers and similarimplantable medical devices. Such features includes, among other things,openings in the sides of the docking cap, reduced edges on the distalend of the docking cap, offset placement of an internal torque feature,and application of a sheath around the main body of the docking cap,each of which facilitates docking of a leadless pacemaker by reducingthe likelihood that the leadless pacemaker will become caught onportions of the leadless pacemaker.

In another embodiment, an improved drive gear and docking cap design isprovided that enables improved docking of the drive gear within thedocking cap and self-aligning of the drive gear with the docking cap tofacilitate more efficient torque transfer. The docking cap includes arecess into which the drive gear is retracted during docking of aleadless pacemaker. The recess and drive gear are shaped such that thedrive gear may be retracted into the recess and subsequently rotated toengage a torque feature of the drive gear with a corresponding torquefeature of the recess. For example, in certain implementations, thetorque feature of the drive gear is a rounded corner of the drive gearand the torque feature of the recess is an internal wall of the dockingcap.

In another embodiment, an atraumatic tip for use with a catheter of aretrieval and/or delivery system is provided. The atraumatic tip may, incertain implementations, include a star-shaped body adapted to expand toaccommodate tissue build up around an implanted leadless pacemaker orsimilar medical device and various sizes of medical devices. Theatraumatic tip may further include radiopaque markers for locating theatraumatic tip during use. Methods of manufacturing such atraumatic tipsare also provided.

Before beginning a detailed discussion of the locking hub and associatedmethod, a general overview of an example leadless pacemaker andcatheter-based delivery system is provided as follows.

A. Overview of Leadless Pacemaker and a Catheter-Based Delivery System

FIGS. 1A-1B illustrate an example leadless cardiac pacemaker 102. Theleadless pacemaker 102 can communicate by conducted communication,representing a substantial departure from conventional pacing systems.The leadless pacemaker can perform cardiac pacing that has many of theadvantages of conventional cardiac pacemakers while extendingperformance, functionality, and operating characteristics with one ormore of several improvements.

In some implementations of a cardiac pacing system, cardiac pacing isprovided without a pulse generator located in the pectoral region orabdomen, without an electrode-lead separate from the pulse generator,without a communication coil or antenna, and without an additionalrequirement of battery power for transmitted communication.

FIG. 1C illustrates an embodiment of a cardiac pacing system 150configured to attain these characteristics. The cardiac pacing system150 includes one or more leadless cardiac pacemakers 102. Each leadlesspacemaker is substantially enclosed in a hermetic housing 151 suitablefor placement on or attachment to the inside or outside of a cardiacchamber, such as the right atrium and/or right ventricle of the patientheart 152, as can be understood from FIG. 1B. Attachment of a leadlesspacemaker to the cardiac tissue can be accomplished via a helical anchor103 on an anchor mount 155 extending from a distal end of the leadlesspacemaker.

As can be understood from FIGS. 1A-1B, the leadless pacemaker 102 canhave two or more electrodes 154, 156 located within, on, or near thehousing 151, for delivering pacing pulses to muscle of the cardiacchamber and optionally for sensing electrical activity from the muscle,and for bidirectional communication with at least one other devicewithin or outside the body. The housing can contain a primary battery toprovide power for pacing, sensing, and communication, for examplebidirectional communication. The housing 151 can optionally containcircuits for sensing cardiac activity from the electrodes 154, 156. Thehousing contains circuits for receiving information from at least oneother device via the electrodes and contains circuits for generatingpacing pulses for delivery via the electrodes. The housing canoptionally contain circuits for transmitting information to at least oneother device via the electrodes and can optionally contain circuits formonitoring device health. The housing contains circuits for controllingthese operations in a predetermined manner.

In some implementations, a cardiac pacemaker can be adapted for deliveryand implantation into tissue in the human body. In a particularembodiment, a leadless cardiac pacemaker can be adapted for implantationadjacent to heart tissue on the inside or outside wall of a cardiacchamber, using two or more electrodes located on or within the housingof the pacemaker, for pacing the cardiac chamber upon receiving atriggering signal from at least one other device within the body.

Leadless pacemakers or other leadless biostimulators are typically fixedto an intracardial implant site by an actively engaging mechanism orprimary fixation mechanism such as a screw or helical member 103 thatscrews into the myocardium. Examples of such leadless biostimulators aredescribed in the following publications, the disclosures of which areincorporated by reference: (1) U.S. Pat. No. 8,457,742, issued on Jun.4, 2013, entitled “Leadless Cardiac Pacemaker System For Usage InCombination With An Implantable Cardioverter-Defibrillator”; (2) U.S.Pat. No. 9,358,400 issued on Jun. 7, 2016, entitled “Leadless CardiacPacemaker”; (3) U.S. Pat. No. 9,216,298, issued on Dec. 22, 2015,entitled “Leadless Cardiac Pacemaker System with ConductiveCommunication”; (4) U.S. Pat. No. 8,352,025 issued on Jan. 8, 2013,entitled “Leadless Cardiac Pacemaker Triggered by ConductiveCommunication”; (5) U.S. Pat. No. 7,937,148 issued on May 3, 2011,entitled “Rate Responsive Leadless Cardiac Pacemaker”; (6) U.S. Pat. No.7,945,333 issued on May 17, 2011, entitled “Programmer for BiostimulatorSystem”; (7) U.S. Pat. No. 8,010,209, issued on Aug. 30, 2011, entitled“Delivery System for Implantable Biostimulator”; and (8) InternationalApplication No. PCT/US2006/040564, filed on Oct. 13, 2006, entitled“Leadless Cardiac Pacemaker and System” and published as WO07047681A2 onApr. 26, 2007.

In addition to the primary fixation mechanism, such as a helix, someleadless biostimulators may further include a secondary fixationmechanism to provide another feature for keeping the leadlessbiostimulator in place within the body. Secondary fixation mechanismscan be either active (e.g., the secondary fixation mechanism canactively engage tissue, either within or outside the heart), or can bepassive (e.g., the secondary fixation mechanism is not attached totissue but rather prevents the leadless biostimulator from moving aroundin the body in the case of accidental detachment). Further details onsecondary fixation mechanisms can be found in U.S. Pat. No. 8,527,068,issued on Sep. 3, 2013.

Leadless pacemakers or other leadless biostimulators can be delivered toand retrieved from a patient using any of the delivery systems describedherein. In some implementations, a leadless pacemaker is attached orconnected to a delivery system and advanced intravenously into theheart. The delivery system can include features to engage the leadlesspacemaker to allow fixation of the leadless pacemaker to tissue. Forexample, in implementations where the leadless pacemaker includes anactive engaging mechanism, such as a screw or helical member, thedelivery system can include a docking cap or key configured to engagethe leadless pacemaker and apply torque to screw the active engagingmechanism into the tissue. In other implementations, the delivery systemincludes clips designed to match the shape of a feature on the leadlesspacemaker and apply torque to screw the active engaging mechanism intothe tissue.

FIG. 1D illustrates a system 100 that may be used for delivery and/orretrieval of a leadless pacemaker 102 into or from a patient. The system100 can include a deflectable catheter 50, a guide catheter 52, and anintroducer sheath 54. As can be understood from FIG. 1D, the deflectablecatheter 50 extends through the guide catheter 52 and includes a distalend and a proximal end. The distal end of the deflectable catheter isselectively connectable to the proximal end of the leadless pacemaker102 and the proximal end of the deflectable catheter includes a handle108 by which the user may cause the deflectable catheter shaft 106 todistally-proximally displace within the length of the guide catheterand, further, by which the user may actuate the distal end of thedeflectable catheter to selectively connect and disconnect from aproximal end of the leadless pacemaker. The deflectable catheter 50 mayextend from both the distal and proximal ends of the guide catheter 52.

The guide catheter 52 extends through the introducer sheath 54 andincludes a distal end and a proximal end. The distal end of the guidecatheter 52 includes a protective pacemaker sheath 104. The proximal endof the guide catheter includes a flush port 114 b extending from aproximal hub 125. The guide catheter 52 extends from both the distal andproximal ends of the introducer sheath 54. The shaft 111 of the guidecatheter 52 may also include one or more sections (not shown) havingdifferent durometers such that the reinforcement and correspondingbending resistance of the sections may be modified according to thespecific application for which the pacemaker system 100 is beingimplemented. The introducer sheath 54 includes a distal end 126 and aproximal end. The proximal end of the introducer includes a flush port114 a and a hub 127.

As can be understood from FIG. 1D and for purposes of discussion, thesystem 100 may be considered to include the various components of thedeflectable catheter 50, the guide catheter 52 and the introducer 54.For example, the system 100 may be considered to include the pacemakersheath 104, the guide catheter shaft 111, the pacemaker introducersheath 107, the handle 108, and the flush ports 114 a, 114 b, and 114 c.The flush ports 114 a, 114 b, and 114 c can be used to flush saline orother fluids through the introducer 54, the guide catheter 52, and thedeflectable catheter shaft 106, respectively. The sheath 107 can beadvanced distally over the catheter shaft 111 to provide additionalsteering and support for the delivery catheter during implantation andto surround the pacemaker as it is introduced through a trocar orintroducer into the patient.

The handle 108 may further include additional elements to manipulate andactuate elements of the system 100. In general, the handle 108 mayinclude elements directed to, without limitation, one or more ofdeflecting the deflectable catheter shaft 106, rotating the deflectablecatheter shaft 106 (and any implantable medical device, such as theleadless pacemaker 102, coupled to the deflectable catheter shaft 106),extending and retracting the leadless pacemaker 102 (or otherimplantable medical device) relative to the protective sheath 104, andengaging or disengaging a coupling mechanism, such as a tether or lasso,to a corresponding feature of the leadless pacemaker 102 to couple theleadless pacemaker 102 to the system 100. For example, the handle 108includes a deflection lever 110 for actuation of the deflectablecatheter shaft 106 and a brake 112 for locking the position or otherwiseincreasing resistance to rotation of the deflection lever 110. Thehandle 108 further includes a docking shroud 114 that may rotated toapply torsion to the deflectable catheter shaft 106, thereby rotatingthe deflectable catheter shaft 106 and the leadless pacemaker 102 whencoupled to the deflectable catheter shaft 106. The docking shroud 114may also translate along the handle 108 to selectively extend andretract the leadless pacemaker 102 from a protective sheath 104 disposedat a distal end of the shaft 111. The handle 108 also includes a releaseknob 116 that, when rotated, causes engagement or disengagement of thecoupling mechanism with the leadless pacemaker 102.

FIG. 2A is a close-up view of a distal portion of a system 200 as usedfor delivery of a pacemaker 202. The pacemaker 202 of FIG. 2A caninclude a helix 203 for attachment of the pacemaker to tissue. In FIG.2A, the pacemaker is attached to a docking cap 218 of a catheter shaft206. The pacemaker sheath 204 is shown pulled back proximally along thecatheter shaft 206 and a guide catheter shaft 211 to expose thepacemaker 202 and the helix 203. In FIG. 2B, the pacemaker sheath 204 isextended distally along the guide catheter shaft 211 to cover thecatheter shaft 206, the pacemaker 202, and the helix 203 to protect thetissue from the sharp edges of the helix 203 during implantation. Whenthe pacemaker sheath 204 is pulled back proximally, as shown in FIG. 2A,the pacemaker 202 is in an exposed, delivery configuration. When thepacemaker sheath 204 is advanced distally to protect the pacemaker 202and the helix 203, as shown in FIG. 2B, the pacemaker 202 is in aprotected, advancement configuration.

FIGS. 3A-3B are close-up and cross sectional views of a pacemaker sheath304 of a system 300 as used for delivery of a leadless pacemaker. Asshown, the pacemaker sheath 304 can include a crease or fold 320 alongthe length of the sheath 304. During initial insertion of the system 300into a patient, a physician can gain access to the patient's venoussystem with an introducer sheath using the Seldinger technique (notshown). The system 300, including the leadless pacemaker and thecatheter shaft, can then be advanced through the introducer sheath intothe patient's venous system to facilitate delivery of the pacemaker intothe heart. Reducing the diameter of the pacemaker, the delivery system,and thus the introducer sheath, provides for easier and less intrusiveaccess to a patient's venous system.

By designing the pacemaker sheath 304 with a fold 320 that runslongitudinally along the sheath, the cross-sectional diameter of thepacemaker sheath 304 can be reduced by folding the sheath 304 overitself. Thus, during initial implantation of the pacemaker through anintroducer sheath into the patient, the pacemaker sheath 304 can bepositioned just proximally to the pacemaker, and folded along fold 320so as to have a cross sectional diameter close to or equal to the samediameter as the pacemaker. This allows a smaller diameter introducersheath to be used than would normally be necessary, since those deliverysystems must incorporate a larger introducer sheath to allow passage ofa full sized pacemaker sheath. After the delivery system is insertedthrough the introducer sheath into the patient, the sheath can beadvanced distally over the leadless pacemaker. Advancing the pacemakersheath 304 distally causes fold 320 to unfold, thereby increasing thediameter of the pacemaker sheath 304 so that it can slide over and coverthe pacemaker and fixation helix. FIG. 3B is a cross-sectional view ofthe pacemaker helix 304 and fold 320, giving another view on how thecross-sectional diameter of the pacemaker sheath 304 can increase anddecrease.

FIG. 4A illustrates a system 400 for delivering a leadless pacemaker,including a pacemaker 402 including a helix 403 and an attachmentfeature 424, and the system 400 including a pacemaker sheath 404, acatheter shaft 406, a docking cap 418, and tethers 422 a, 422 b. Thetethers 422 a, 422 b can include wires, shafts, tubes, cords, ropes,strings, or other similar structures that can extend throughout thecatheter shaft 406. In some implementations, the tethers 422 a, 422 binclude a shape memory material, such as nitinol. In otherimplementations, the tethers include stainless steel wires or braids. InFIG. 4A, the pacemaker 402 is not attached to docking cap 418 of thedelivery catheter. The process of connecting the pacemaker to thedelivery catheter will now be described.

Referring to FIG. 4B, tethers 422 a and 422 b can include distalfeatures 426 a, 426 b. The distal features 426 a, 426 b can be, forexample, features on the tethers that protrude radially from the tether,such as bumps, spheres, cylinders, rectangles, or other similar shapesextending outwards from the tethers. In some implementations, the distalfeatures can be expandable, such as balloons or expandable mechanicalstructures. Generally, the distal features have a cross sectionaldiameter larger than the cross sectional diameter of the tethers. Asshown, in one embodiment, the distal feature 422 a can be advancedfurther from the catheter than the distal feature 422 b, so that whenthe tethers are pushed together, the distal feature 422 b rests againstthe tether 422 a. This causes the combined cross sectional diameter ofboth distal features and tethers to be less than if the distal featureswere lined up side by side. By way of comparison, in FIG. 4C the distalfeatures 426 a, 426 b are lined up side by side and therefore have agreater combined cross sectional diameter when pressed together than isshown in FIG. 4B.

The length of the tethers 422 a, 422 b and thus the position of thedistal features 426 a, 426 b, can be adjusted so that the distalfeatures 426 a, 426 b are not aligned in a side by side configuration(e.g., the un-aligned configuration shown in FIGS. 4A-4B). When thetethers and distal features are in this unaligned configuration, thecross sectional diameter of the distal features is reduced since thedistal features are not positioned side by side. The tether distalfeatures 426 a, 426 b can then be advanced in this un-alignedconfiguration through a hole 428 of an attachment feature 424 of theleadless pacemaker, as shown in FIGS. 4D-4F. In this implementation, thediameter of the hole 428 should be sufficiently large enough to avow thedistal features 426 a, 426 b of the tethers 422 a, 422 b to pass when inthe un-aligned configuration. Upon passing the distal features throughthe hole 428, the length of the tethers 422 a, 422 b can then beadjusted to align the distal features 426 a, 426 b in the side by sideconfiguration (e.g., as shown in FIGS. 4C and 4E). When the distalfeatures 426 a, 426 b are positioned side by side, the combined crosssectional diameter of the distal features 426 a, 426 b becomes largerthan the diameter of the hole 428, which essentially locks the tethers422 a, 422 b and distal features 426 a, 426 b in the attachment feature424 be preventing the distal features 426 a, 426 b from being able topass proximally through the hole 428.

Still referring to FIGS. 4C and 4D, the docking cap 418 of the deliverycatheter can include a torque slot 430 (shown in FIG. 4C) sized andconfigured to mate with a torque key 432 (shown in FIG. 4D) disposed ona proximal end of the pacemaker. The torque slot 430 can be coupled to atorque shaft 431, which runs the length of the delivery catheterextending into the handle (not shown). In FIGS. 4C and 4D, torque key430 is shown as a “male” key and torque slot 430 is shown as a “female”key, but it should be understood that in other implementations, the“male” key can be located on the attachment feature 418, and the“female” key can be disposed on the pacemaker. It should also beappreciated that key 432 and slot 430 can include any number of shapes,such as square, rectangle, triangle, pentagon, hexagon, cross, “X”,etc., so long as key 432 fits within and can apply rotational torque toslot 430. Once the tethers are locked within the attachment feature, thetethers can be pulled proximally to pull attachment feature 424 and thepacemaker towards the catheter and to attach the pacemaker to thedelivery catheter, thereby engaging torque slot 430 with torque key 432(as shown in FIG. 4G).

FIG. 5A illustrates a close-up view of one embodiment of a distalportion of the system 100 shown in FIG. 1 as used for retrieval of aleadless pacemaker 502. The distal portion of the retrieval catheter caninclude a snare 503 configured to grasp a leadless cardiac pacemaker orother medical device, and a docking cap 504 configured to allow dockingof the leadless pacemaker 502 with the retrieval catheter after engagingthe pacemaker 502 with the snare 503. FIG. 5A also illustrates acatheter shaft 506 terminating at the docking cap 504, and a protectivesheath 507 positioned along the catheter shaft 506 slightly proximal tothe docking cap 504 and the leadless pacemaker 502.

As shown in FIG. 5A, the snare 503 can include at least one loop 516extending from the catheter shaft 506. As the snare 503 is advanceddistally out of the system 100 from the docking cap 504, the loops 516can expand in size to aid a user in positioning the snare 503 around orin proximity to the pacemaker 502 to be retrieved. In someimplementations, as in FIG. 5A, the snare 503 can include multipleloops, such as three loops. However, any number of loops can be used aslong as the catheter shaft contains sufficient volume to accommodate theloops.

In another embodiment, as shown in FIG. 5B, the snare can include only asingle loop. Also shown in FIG. 5B, the loops can include any number offeatures 518 to aid in grasping a pacemaker or medical device forretrieval. In FIG. 5B, the feature 518 can include, for example, a notchfeature. In some implementations, the loops of the snare can bepositioned off axis from the center of the catheter shaft to aid inkeeping the pacemaker in line with the catheter during removal. Forexample, in FIG. 5B, the single loop snare 503 can include a notchfeature 518 and be positioned off axis from the longitudinal axis of thecatheter shaft 506. Since the snare is off axis from the catheter, thesnare 503 can be looped around a retrieval feature 520 of the pacemakerby positioning the catheter adjacent to the pacemaker and allowing theloop to come into contact with the housing of the pacemaker. As thecatheter is pulled away from the pacemaker, the snare 503 can slide upthe pacemaker, and the notch feature 518 can be allowed to engage theretrieval feature 520 of the pacemaker.

FIG. 5C illustrates the snare 503 grasping a retrieved feature 520 ofthe leadless cardiac pacemaker 502. In the illustrated embodiment, asnare locking sleeve 505 can be advanced distally over the snare fromthe docking cap 504 of the catheter. As the snare locking sleeve 505advances distally along the snare 503, it can cause the loops of thesnare 503 to reduce in size, thereby grasping or locking onto theretrieval feature 520 of the pacemaker 502. In some implementations, thesnare locking sleeve 505 can also include a torque shaft that runsthrough the length of the catheter. Details of the torque shaft will bedescribed in more detail below, but generally the torque shaft can berotated independently of the catheter shaft and coupled to the dockingcap 504 of the catheter to apply rotational torque to the docking cap,and thus, to a pacemaker or medical device to be retrieved. Inimplementations where the snare 503 includes a plurality of loops, itmay be more likely that one of the loops will grasp the pacemaker thanin implementations where the snare 503 includes only a single loop.

Following capture and locking of the snare 502 with the leadlesspacemaker 502, the leadless pacemaker may be docked within the dockingcap 504. As previously discussed. FIG. 4G illustrates a delivery systemin which a leadless pacemaker 402 is retained in a docked position. Theconfiguration illustrated in FIG. 4G may be substantially similar to aconfiguration in which the leadless pacemaker 402 is docked with adocking cap 418 of a retrieval system. Accordingly, in addition toillustrating docking in a delivery system. FIG. 4G may also beinterpreted to illustrate a close-up view of a distal portion of aretrieval catheter with a snare locked onto a retrieval feature (notshown) of the leadless pacemaker 402 and docked within docking cap 418.In some implementations, as will be described in more detail below, thedocking cap 418 can include a key or interference feature configured tomate with and engage a corresponding key or feature on the pacemaker402. In some implementations, the key or slot on the docking cap 418 canmatch a unique shape or feature of the retrieval feature of thepacemaker 402. Because the key or slot on or in the docking cap 418 canmate with and engage the key or slot on the pacemaker, the retrievalcatheter can be configured to apply torque to the pacemaker to unscrewand remove the pacemaker from tissue. FIG. 4G also illustrates aprotective sheath 407 positioned slightly proximally to the docking cap418 along the catheter shaft of the retrieval system.

As shown in FIG. 4G, the docking cap 418 can include ball bearings 409which allow the docking cap to be free-rotating from the rest of thecatheter shaft. This effectively reduces the removal torque andadditional forces from the catheter body. The docking cap 418 can beselectively coupled to a torque shaft (not shown) that extends throughthe length of the catheter to a torque knob on the handle (describedbelow) or other rotatable portion of the handle coupled to the torqueshaft. When the torque shaft is coupled to the docking cap 418, rotationor actuation of the torque knob rotates the torque shaft, therebyrotating the docking cap 418 at the end of the retrieval catheter. Insome implementations, the docking cap 418 can include a keyed portion orinterference feature so as to apply additional torque to the pacemakerwhen unscrewing.

Referring back to FIG. 2B, a protective sheath 204 is shown disposedover a leadless cardiac pacemaker and positioned at the distal end ofguide catheter shaft 211. As described above, the protective sheath canbe configured to slide over the pacemaker to prevent any sharp edges orfeatures of the pacemaker from tearing, damaging, or catching ontotissue during removal of the pacemaker. The protective sheath can beslidable along a longitudinal axis of the catheter so as to allow forcovering and uncovering of the pacemaker with the sheath. In someimplementations, the protective sheath can include other form factorsthan illustrated in FIG. 2B. For example, in some retrieval scenarioswhere vegetative growth over the device is significant, the protectivesheath may be of a larger diameter to accommodate the increase in sizeof the device.

The above description of FIGS. 5A-5C can be used to illustrate oneembodiment of a method of retrieving a medical device or leadlesscardiac pacemaker from a patient. First, a retrieval catheter can beadvanced into a patient until the docking cap of the catheter is in thevicinity of the pacemaker. Next, the snare of the retrieval catheter canbe advanced distally outward from the catheter to surround the retrievalfeature of the pacemaker. Once the snare is surrounding the retrievalfeature of the pacemaker, the snare locking sleeve/torque shaft can beadvanced distally along the snare to close the snare, causing the snareto grasp the retrieval feature of the pacemaker. Next, the snare andsnare locking sleeve can be pulled proximally towards the docking cap ofthe catheter so as to engage the proximal end or retrieval feature ofthe pacemaker. Rotational torque can then be applied by the catheter tothe pacemaker via the torque shaft and docking cap to unscrew thepacemaker from the tissue. The protective sheath can be advanced overthe pacemaker, and the pacemaker can then be removed from the patient.

FIGS. 6-8B show multiple views of various implementations of retrievalfeatures on a leadless cardiac pacemaker. The retrieval featuresillustrated in these figures can be grasped by the snare of theretrieval catheters described herein, and can also be configured to dockwithin the docking cap of the retrieval catheter.

In FIGS. 6-7, the retrieval feature includes a “button” or circulargrasping feature 732. The grasping feature 732 can be attached to thepacemaker 702 via at least one flexible stem 734. The flexible sternallows for easier capturing of the pacemaker into the docking cap byallowing the grasping feature and stem(s) to “bend” into the docking capwhen the retrieval catheter is off-axis from the pacemaker during aretrieval attempt. The flexible stem(s) also allow the grasping feature732 to orient itself within the snare and to compensate for theasymmetry of the snare to allow it to align the docking cap with thepacemaker. Additionally, the flexible stem deflection permits torquetransmission from the catheter to the leadless pacemaker. The flexiblestem can be made of materials such as nitinol, stainless steel ortitanium cable, MP35N, or other similar materials. The flexible stem maybe connected to the grasping feature and the proximal end of theleadless pacemaker by laser welding, soldering, or other manufacturingprocesses know in the art.

Also shown in FIG. 6, a proximal portion of the pacemaker 702 caninclude a key feature 736. The key feature 736 can be sized andconfigured to mate with the interference feature within the docking cap,as described above. The key feature of the pacemaker and theinterference feature of the docking cap and catheter can allow thetorque shaft and docking cap of the catheter to apply rotational torqueto the pacemaker, such as to unscrew the pacemaker from tissue duringretrieval.

FIGS. 8A-8B illustrate another embodiment of a “hook shaped” retrievalfeature 832 on the pacemaker 802. The hook shaped proximal cap can allowfor easier grasping by the snare. The “hook shaped” retrieval featurecan provide an easily accessible yet atraumatic surface for the snare tograsp. In some implementations, a base portion 834 of the hook shapedfeature can include a flexible material, as described above with respectto the flexible stems of the “button” shaped retrieval feature in FIGS.6J. The hook shaped retrieval feature can also include cutouts 838 thatcan serve a similar purpose to the key feature described above in FIGS.6-7. The cutouts can engage, for example, similarly shaped features inthe docking cap or retrieval catheter to allow the catheter to applyrotational torque to the pacemaker for unscrewing the pacemaker fromtissue.

As described above, the docking cap itself can include cutouts orrecessed slots configured to mate with or engage the retrieval featureof the pacemaker. For example, the circular retrieval feature of FIGS.6-7 can mate with a similarly shaped recessed slot within the dockingcap. Similarly, the hook shaped retrieval feature of FIGS. 8A-8B canmate with a similarly shaped recessed slot within the docking cap.

B. Catheter Delivery System Handle Including Deflection Lever and LeverBrake Systems

Catheter delivery and retrieval systems including catheters havingdeflectable or steerable tips generally include a mechanism on a handlethat actuates or otherwise causes the deflection of the catheter tip. Ingeneral, such mechanisms include a pull wire coupled to each of themechanism and the deflectable tip such that actuation of the mechanismpulls the pull wire, thereby causing deflection of the tip.

Conventional actuation mechanisms for deflectable tips have variousdisadvantages and shortcomings. First, such conventional mechanismsoffer little to no mechanical advantage such that the user must exert aforce on the actuation mechanism that is substantially equal to theforce required to deflect the catheter tip. Such forces may result inexcess fatigue during lengthy procedures and/or may be difficult to usewith larger catheters or by users with relative small hands. Second,many conventional deflection mechanisms require two hands to operate.Finally, operation of many conventional deflection mechanisms is notintuitive or immediately apparent from the appearance of the mechanism.

In light of the foregoing, the present disclosure provides delivery andretrieval systems having deflectable catheters and that further includeimproved actuation and locking mechanisms.

In one embodiment, the delivery and retrieval system includes a handleand a lever extending from the handle. The lever is coupled to a hubthat is in turn coupled to a deflectable catheter tip by a pull wire. Bydepressing the lever against the handle, the hub may be rotated, puffingthe pull wire and deflecting the catheter tip. In certainimplementations, the handle may further include a braking or lockingmechanism that may be actuated to lock the hub in position or otherwiseincrease resistance to further rotation or counter-rotation of the hub.In certain implementations, the deflection lever disclosed hereinprovides significant mechanical advantage such that the input forcerequired to be exerted by a user is reduced relative to the forceexerted by the mechanism on the pull wire. For example, in certainimplementations the force required to move the deflection lever may beapproximately thirty to fifty percent of the force required to move thedeflectable catheter directly.

FIGS. 9A-9B are top views of an embodiment of a handle 900 of a deliveryand/or retrieval system, such as the system 100 of FIG. 1D. The handle900 includes a housing 902 into which a deflectable catheter 50 isinserted. The deflectable catheter includes a deflectable section 51which may correspond to a tip section of the deflectable catheter 50. Inother implementations, the deflectable section 51 may instead correspondto a different section of the deflectable catheter 50 proximal the tipsection.

The handle 900 includes a deflection lever 904 extending from thehousing 902. In FIG. 9A, the deflection lever 904 is shown in anextended position. The extended position generally corresponds to aresting position of the deflection lever 904, such as when no externalforce is applied to the deflection lever 904. In the resting position,the deflectable section 51 of the deflectable catheter 50 is in aresting position, which in the example of FIG. 9A is a substantiallystraight configuration. In contrast to FIG. 9A. FIG. 9B illustrates thedeflection lever 904 in a depressed position. As the deflection lever904 is transitioned between the extended and depressed positions, thedeflectable section 51 transitions between the resting configurationillustrated in FIG. 9A and the deflected configuration illustrated inFIG. 9B, which in the current example, is a ninety degree deflection inthe direction of the deflection lever 904. Accordingly, the deflectionlever 904 may be partially depressed in order to achieve configurationsof the deflectable section 51 intermediate to those illustrated in FIGS.9A-9B.

FIGS. 10A-10C are bottom views of the handle 900 with a portion of thehousing 802 removed to show internal components within the handle 900.FIGS. 10A and 10B, for example, illustrate the handle 900 with thedeflection lever 902 in an extended and depressed configuration,respectively, which generally correspond to the extended and depressedconfigurations illustrated in FIGS. 9A-9B.

The length of the lever 904 may be varied to modify the degree ofmechanical advantage provided by the lever 904 to cause deflection ofthe deflectable catheter. Referring to FIG. 10A, for example, the lever904 may define a moment arm 905 extending from the center of the hub 906to the end of the lever 904. In certain implementations, the moment arm905 is from and including 3.00 inches and including 4.00 inches. Forexample, in one specific implementation, the moment arm 905 is 3.50inches. The lever 904 may also extend from the hub 906 at apredetermined angle 907 relative to a longitudinal axis 911 of thehandle 900 when the lever 904 is in the extended position. In certainimplementations, the angle 907 is from and including 50 degrees to andincluding 60 degrees. For example, in one implementation, the angle is57 degrees. Also, full depression of the lever 904 may result in apredetermined rotation of the hub 906. For example, in certainimplementations, movement of the lever 904 from the extended position(as illustrated in FIG. 10A) to the depressed position (as illustratedin FIG. 10B) may result in rotating the hub 906 from and including 35degrees to and including 50 degrees. For example, in certainimplementations movement of the lever 904 from the extended position tothe depressed position may rotate the hub 906 approximately 45 degrees.

As shown in FIGS. 10A-10C, the deflection lever 904 may be coupled to ahub 906 supported within the housing 902 that rotates within the housing902 in response to depression of the deflection lever 904. A fiber 909couples the hub 906 to a pull wire 908 extending from the deflectablesection 51 of the deflectable catheter 50 (shown in FIGS. 9A-9B) that,when pulled, causes deflection of the deflectable section 51.

In general, the fiber 909 is coupled to the hub 906 at an anchor 910,which may include a press pin 912, set screw, or similar fixationmechanism for fixing the fiber 909 relative to the hub 906. The housing902 and the hub 906 may also include additional structural elements forrouting and supporting the fiber 909. For example, the housing 902 mayinclude a roller 914 over which the fiber 909 is routed to reducefriction. The hub 906 may also include one or more curved or arced walls916 over which the fiber 909 is wrapped. In certain implementations, thetotal travel of the fiber 909 and, by extension, the pull wire 908 isincreased by having the fiber 909 wrap around the outside of the arcedwalls 916 as opposed to following a straight line between the roller 914and the anchor 910. In certain implementations, the arced wall 916 maybe disposed at a radius from and including 0.600 inches to and including0.900 inches and have an arc length from and including 0.350 inches toand including 0.550 inches. For example, in one implementation, thearced wall 916 may be disposed at a radius of 0.787 inches and have anarc length of approximately 0.484 inches.

Referring to FIG. 10C, the handle 900 may further include a multiplierpost 920 about which the fiber 909 is wrapped. In certainimplementations, for example, the multiplier post 920 may be coupled tothe housing 902 and extend through a post cutout 922 defined by the hub906. When the multiplier post 920 is used, the fiber 909 is routedaround the arced walls 916 and further around the multiplier post 920such that the path followed by the fiber 909 is a longer and moreserpentine as compared to implementations in which the multiplier post920 is absent or unused (such as illustrated in FIGS. 10A-10B).

Aspects of the hub 906 may conform to specific ranges of predeterminedvalues. For example, in certain implementations, the arced wall 916 isdisposed at a first radius 917 relative to the center of the hub 906.For example, the first radius 917 may be from and including 0.55 inchesto and including 0.81 inches. The arced wall 916 may also extend along apredetermined arc length. In certain implementations, the predeterminedarc length may be from and including 0.25 inches to and including 1.25inches. Similarly, the multiplier post 920 may be disposed at a secondradius 919 from and including 0.405 inches to and including 0.465 inchesfrom the center of the hub 906.

Referring now to FIGS. 11A-11B, the handle 900 may further include abrake assembly 950 disposed opposite the deflection lever 902. Incertain implementations, the brake assembly 950 may include a knob 952from which a brake lever 954 extends. During operation, the brakeassembly 950 may be actuated to increase resistance to rotation of thehub 906 and the deflection lever 902 coupled thereto. More specifically,by applying a force to the brake lever 954, the knob 952 may be rotatedsuch that the brake assembly 950 is movable between a first position,shown in FIG. 11A, in which a low resistance (including no resistance)is applied to the hub 906 and a second position, shown in FIG. 11B, inwhich a high resistance is applied to the hub 906. Although shown asbeing moved between the first and second positions when the deflectionlever 902 is in the depressed position, the brake assembly 950 may beactuated when the deflection lever 902 is disposed in any position. Bydoing so, the deflection lever 902 may be held by the brake in anintermediate position and, by extension, the deflection section 51 maybe held in a partially deflected configuration. In certainimplementations, movement of the brake assembly 950 between the firstand the second positions includes rotating the knob 950 from andincluding 0 degrees to and including 65 degrees.

FIG. 12 is a cross-sectional view of the handle 900 including the brakeassembly 950. In certain implementations, the brake assembly 950 mayinclude a threaded insert 956 coupled to the knob 952 and threadedlycoupled to a threaded shaft 958. The threaded shaft 958 extends throughan exterior brake washer 966, a hole 960 defined by the housing 902, andan unthreaded hub washer 962 and terminates in a shaft end 964 that isrotationally fixed within the housing 902. The washer 962 is disposedwithin the hub 906 and is rotationally fixed relative to the hub 906.For example, in certain implementations, the washer 960 may be ahexagonal washer 962 and may be disposed within a hexagonal hole orreceptacle 964 defined by the hub 906.

As previously discussed, a braking force applied by the brake assembly950 and the resulting resistance to rotation of the deflection lever 904and the hub 906 may be adjusted by rotating the brake assembly 950 and,more specifically, the knob 952 by moving the brake lever 954. In theimplementation illustrated in FIG. 12, the braking force/resistance is aresult of friction caused by compression of the exterior wall 960between the brake washer 966 and the hub washer 962. For example, whenincreasing the braking force/resistance, rotation of the knob 952 causesthreaded translation of the threaded insert 956 towards the shaft end962 of the threaded shaft 958. As a result of the translation, theexterior wall 960 is compressed between the brake washer 966 and the hubwasher 962. This compression increases the frictional force on the hubwasher 962 and, as a result, the resistance to rotation of the hub 906as a result of the hub washer 962 being rotationally fixed relative tothe hub 906. By varying the degree to which the knob 952 is rotated, thecompressive force applied to the exterior wall 960 and the resultingfrictional force on the hub washer 962 may be modified as required bythe user.

In certain implementations, the knob 952 may be rotated into anintermediate position between the first position (as illustrated in FIG.11A) and the second position (as illustrated in FIG. 11B). In such anintermediate position, a corresponding intermediate resistance isapplied to the hub 906 such that a reduced amount of force is requiredby the user of the handle 900 to maintain the hub 906 in its currentposition. So, if a user anticipates that some but relatively infrequentmovements of the hub 906 are required but that the hub 906 willprimarily be held static, an intermediate resistance may be appliedusing the braking assembly 950 such that the user is still able torotate the hub 906 if needed but the overall force required to maintainthe position of the hub 906 is reduced.

In certain implementations, the deflectable catheter 50 may be biasedtoward an undeflected position such that the handle 900 has a passivereturn feature. In such implementations, an intermediate position of theknob 952 may also be used to apply sufficient resistance to overcome thepassive return of the deflectable catheter 50 without otherwisepreventing deflection by movement of the lever 904.

The handle 900 illustrated in the example implementations of FIGS. 9A-9Band 11A-11B is shown in a primarily right-handed configuration. Whenoperated using the right hand, the user grips the handle 900 in anoverhand grip such that the user's thumb extends in the direction of thecatheter 50. When gripped in this manner, the user is able to readilysqueeze the handle 904 with his or her fingers and manipulate the brakeassembly 950 with his or her thumb. Moreover, the general layout of thehandle 900 with the handle 904 extending away from the user results inan intuitive design in which a user is more likely to inherentlyunderstand that depressing the lever 904 results in deflection of thetip 51 away from the user. Such intuition is further reinforce Incertain implementations by the presence of flush ports (such as theflush ports 114 a-114 c shown in FIG. 1D) which generally extend awayfrom the user.

Although the handle 900 is shown in a configuration intended for usewith an overhanded right hand grip, the handle 900 may nevertheless beoperated using other grips including an underhand right hand grip andeither an over- or underhand left hand grip. For example, in anunderhand left handed grip, the user's thumb would still be directedtowards the catheter 50 such that the user can readily manipulate eachof the handle 904 and the brake assembly 950 using one hand. With anunderhand right hand grip or an overhand left hand grip, the user maystill be able to depress the lever 904, however, the user may requiretheir other hand or an assistant to manipulate the brake assembly 950.

In still other implementations, a configuration intended for use with anoverhand left hand grip may be achieved by flipping the lever 904 suchthat the lever 904 extends in the distal direction. In suchimplementations, depression of the lever 904 would cause the hub 906 torotate in the opposite direction as in the implementation illustrated inFIGS. 9A-9B. Accordingly, to maintain proper tensioning of thedeflectable tip, the fiber wire 909 adapted to pull the deflectable tipmay be coupled to the top side of the hub 906 as opposed to the bottomside of the hub 906 as illustrated in FIGS. 10A-10C. The arced wall 916and multiplier post 920 could also extend from the top of the hub 906 insuch implementations. The brake assembly 950 may also be reversethreaded such that that increasing the resistance provided by the brakeassembly 950 is achieved by rotating the brake lever 954 in acounterclockwise direction, opposite that illustrated in FIGS. 11A-11B.

The foregoing are merely examples of ways in which the handedness of thehandle 900 may be modified in order to accommodate a left- orright-handed user. Moreover, any of the foregoing examples may besubstantially mirrored or otherwise modified in order to produce eithera left- or right-handed configuration.

C. Catheter Delivery System Handle Including Adjustable TensioningSystem

As previously described in the context of FIGS. 1A-1D, leadlesspacemakers are anchored into the endocardium using one or more fixationmechanisms. Such fixation mechanisms may include, without limitation,one or more of a helical screw and tines extending from the distal endof the leadless pacemaker.

During delivery and implantation of a leadless pacemaker, firm couplingbetween the leadless pacemaker and the corresponding delivery system isrequired such that torque applied using the delivery system istransmitted to the leadless pacemaker. Firm coupling between theleadless pacemaker and a retrieval system is also critical in the eventthat the leadless pacemaker is to be subsequently relocated or removedfrom the patient. For example, during the intervening time periodbetween implantation and retrieval, features of the leadless pacemakermay become encapsulated by tissue. In certain cases, for example, matingfeatures of the leadless pacemaker may become partially or entirelyencapsulated by tissue and the ability of a physician to couple acatheter of the retrieval system to the mating features may becompromised. As a result, torque transmission from the retrieval systemto the leadless pacemaker may be poor and may result in an inability toretrieve the leadless pacemaker.

To address the foregoing issue, a tensioning assembly for use in ahandle of a retrieval system is provided that allows a user to obtainand maintain tension on a captured and docked leadless pacemaker. As aresult, the contact force between a docking cap or other distal featureof a retrieval catheter of the retrieval system is increased and torquetransmission between a torque shaft of the retrieval system and theleadless pacemaker is improved as compared to conventional retrievalsystems. The tensioning assembly is auto-locking, thereby preventing auser from accidentally losing grip on a leadless pacemaker once capturedand, in particular, during unscrewing of the leadless pacemaker from theendocardium. In addition to the foregoing issues related to tissueencapsulation, the tensioning assembly described herein alsoaccommodates variations in patient anatomy (such as, without limitation,variations in vascular bend angles) and variations in catheter systemcomponents.

By incorporating the tensioning assembly into the handle, a user is ableto obtain and maintain a firm grip on the leadless pacemaker beingretrieved. Moreover, if the retrieval catheter is slipping on theleadless pacemaker as the retrieval catheter during unscrewing of theleadless pacemaker from the endocardium or if the user notices a gapbetween the retrieval catheter and the pacemaker as a result of tissueor system variation, the user may readily increase tension on theleadless pacemaker. The auto-locking feature maintains tension on theleadless pacemaker and may further provide feedback to the user, suchaudible or tactile feedback, as tension is increased.

Tensioning assemblies in accordance with this disclosure generallyinclude a handle having a pair of handle portions that are movablerelative to each other and coupled by a ratchet mechanism. For example,in one implementation, the handle includes a first, outer handle portionwithin which a second, inner handle portion may be inserted andtranslated. The first handle portion includes a pawl that interacts witha rack surface of the second handle portion thereby forming a ratchetmechanism that couples the first handle portion to the second handleportion.

The second handle portion is coupled to a snare or similar retrievalfeature such that as the second handle portion is proximally translatedrelative to the first handle portion, the retrieval feature is cinchedor otherwise closed, such as by retraction of the snare into a torque orretrieval catheter. As the second handle portion is translated, theratcheting mechanism engages to ensure that tension is maintained on theretrieval feature even if the user releases his or her grip on thesecond handle portion or otherwise reduces tension applied to the secondhandle portion.

In certain implementations, the pawl of the first handle portion iscoupled to and rotatable about a pin disposed within the first handleportion. In such implementations, the pawl may include a buttonextending through the housing of the first handle portion and may bebiased, such as by a spring, into contact with the rack of the secondhandle portion. To release the pawl from the rack, a user may depressthe button, thereby causing the pawl to rotate about the pin,disengaging the pawl from the rack, and allowing distal translation ofthe second handle portion relative to the first handle portion.

The rack of the second handle portion includes multiple teeth thatextend around the circumference of the second handle portion. As aresult, the second handle portion may be rotated relative to the firsthandle portion while tension is maintained on the snare by the ratchetmechanism.

FIGS. 13A-13C are cross-sectional side views of one embodiment of atensioning assembly 1300 for use in a retrieval system, such as thedelivery and retrieval system 100 illustrated in FIG. 10. The tensioningassembly 1300 is generally disposed within a handle 1302 of theretrieval system and couples a distal handle portion 1304 to a proximalhandle portion 1306. As illustrated in FIGS. 13A-13C, the proximalhandle portion 1306 includes a shaft 1307 that extends at leastpartially into the distal handle portion 1304. The proximal handleportion 1306 is coupled to a tensioning member 1309, such as a wire,that extends from the handle 1302 and to a distal end of the retrievalsystem where the tensioning member 1309 may be coupled to a snare, atether, a lasso, or similar retrieval feature 1311 couplable to acorresponding retrieval feature of an implantable medical device, suchas a leadless pacemaker.

The distal handle portion 1304 and the proximal handle portion 1306 arecoupled together by a ratchet mechanism 1308 that includes one or morepawls 1310 a, 1310 b of the distal handle portion 1304 and a rack 1312disposed on the shaft 1307. The rack 1312 includes multiple teeth, suchas tooth 1314. As illustrated by the transition between FIGS. 13A-13C,the proximal handle portion 1306 may be translated proximally relativeto the distal handle portion 1304 such that the pawls 1310 engage theteeth of the rack 1312.

During operation, a user of the retrieval system including thetensioning assembly 1300 loosely couples the retrieval feature 1311 tothe implantable medical device. Once loosely coupled, the proximalhandle portion 1306 is translated proximally which applies tension tothe tensioning member 1309 and tightens the coupling between theretrieval system and the implantable medical device. For example, asillustrated in the transition from FIG. 13A to FIG. 13C, increasingtension on the tensioning member 1309 may cinch or otherwise tighten theretrieval feature 1311. For example, as illustrated in FIGS. 13A-13C,the retrieval feature 1311 may be disposed and translatable within acatheter shaft 1313, the catheter shaft 1313 being coupled to a distalhandle portion 1304 or other portion of the handle fixed relative to theproximal handle portion 1306. Accordingly, as the proximal handleportion 1306 is translated proximally relative to the distal handleportion 1304, the retrieval feature 1311 is similarly translatedproximally such that the retrieval feature 1311 is drawn into thecatheter shaft 1311. By further translating the proximal handle portion1306, the retrieval feature 1311 is further drawn into the cathetershaft 1313. Alternatively, if an object, such as an attachment featureof a leadless pacemaker, is retained within the retrieval feature 1311,further translation of the proximal handle portion 1306 causes theretrieval feature to close more tightly around the object, increasingtension on the tensioning member 1309.

The pawls 1310 a, 1310 b and the teeth 1314 are shaped such that whenthe proximal handle portion 1306 is sufficiently translated in theproximal direction, the pawls 1310 a, 1310 b engage the teeth 1314 ofthe rack 1312 due to the pawls 1310 a, 1310 b being biased intoengagement with the rack 1312. The rack 1312 defines a locking region ofthe tensioning assembly 1300 due to the ratcheting mechanism 1308 and,more specifically, by the shape and arrangement of the teeth 1314.Accordingly, once the pawls 1310 a, 1310 b engage the teeth 1314 of therack 1312, subsequent distal translation of the proximal handle portion1306 relative to the distal handle portion 1304 is resisted orprevented. However, as illustrated by the transition from FIG. 13B toFIG. 13C, the proximal handle portion 1306 may be further translated ina proximal direction, thereby applying further tension on the tensioningmember 1309. Such further tensioning of the tensioning member 1309 maybe required to overcome one or more sources of variation that can impactthe contact/grip force between the catheter retrieval system and theimplantable medical device and ultimately torque transmission betweenthe catheter retrieval system and the implantable medical lead. Forexample, such sources of variation may include, without limitation,variations in patient anatomy resulting in varying bend and approachangles, the severity of tissue encapsulation on coupling features of theimplantable medical device, and variations in the shape and propertiesof components of the catheter retrieval system.

The pawls 1310 a, 1310 b may include respective buttons 1316 a, 1316 badapted to disengage the pawls 1310 a, 1310 b from the rack 1312 whendepressed, thereby allowing distal movement of the proximal handleportion 1306 relative to the distal handle portion 1304. For example,the pawls 1310 a, 1310 b of FIGS. 13A-13C include buttons 1316 a, 1316 bthat, when depressed, cause the pawls 1310 a, 1310 b to rotate aboutrespective mounting pins 1318 a, 1318 b by which the pawls 1310 a, 1310b are coupled to the distal handle portion 1304. In certainimplementations, the mounting pins 1318 a, 1318 b may be mechanicallypressed or free floating within the distal handle portion 1304 andvarying the location of the mounting pins 1318 a, 138B within the distalhandle portion 1304 may vary the degree of mechanical advantage when thebuttons 1316 a, 1316 b are depressed. Rotation of the pawls 1310 a, 1310b about the mounting pins 1318 a, 1318 b disengages the pawls 1310 a,1318 b from the teeth 1314 of the rack 1312, thereby enabling distaltranslation of the proximal handle portion 1306.

The buttons 1316 a, 1316 b may be one of flush with, protruding from, orrecessed relative to the distal handle portion 1304. In certainimplementations, the position of the buttons 1316 a, 1316 b relative tothe distal handle portion 1304 may vary depending on whether the pawls1310 a, 1310 b are engaged with or disengaged from the rack 1312. Forexample, in one implementation, the buttons 1316 a, 1316 b may berecessed prior to proximal movement of the proximal handle portion 1304that engages the ratchet mechanism 1318. However, after engagement, thebuttons 1316 a, 1316 b may protrude from the distal handle portion 1304to facilitate depression of the buttons 1316 a, 1316 b. The relativeposition of the buttons 1316 a, 1318 b to the distal handle portion 1304may be controlled by, among other things, the size and the shape of thepawls 1310 a, 1310 b, the depth and shape of the teeth 1314 of the rack1312, and the position of the mounting pins 1318 a, 1318 b about whichthe pawls 1310 a, 1310 b rotate.

As illustrated in FIGS. 13A-13C, the rack 1312 may extend about thecircumference of the shaft 1307 such that the proximal handle portion1306 may be rotated without disengaging the pawl 1310 from the rack1312. As a result, a user may rotate the proximal handle portion 1306 tounscrew the leadless pacemaker or similar implantable medical devicewithout compromising the coupling between the retrieval system and theimplantable medical device. Also, during unscrewing of the implantablemedical device, if the user notices a loosening of the coupling to theimplantable medical device, the user may simply translate the proximalhandle portion 1306 in the proximal direction to apply further tensionwithout modifying the rotational position of the proximal handle portion1306 relative to the distal handle portion 1304.

In certain implementations, the ratchet mechanism 1308 may be configuredto provide tactile and/or audible feedback to a user of a retrievalsystem implementing the tensioning assembly 1300. Such feedback may comein the form of an audible click or tactile bump as the proximal handleportion 1306 is translated proximally and the pawls 1310 engagesuccessive teeth 1314 of the rack 1312.

The performance characteristics of the tensioning assembly 1300 may bemodified by, among other things, adjusting aspects of the rack 1312including, without limitation, the quantity, spacing, and geometry ofthe teeth 1314. For example, the quantity of teeth 1314 and length ofthe rack 1312 may be adjusted to accommodate expected amounts ofvariation based on the operation undertaken using a retrieval systemincluding the tensioning assembly 1300. Spacing between adjacent teethof the rack 1312 may also be modified to change the resolution by whichthe tension applied and maintained by the tensioning assembly 1300 maybe modified. The angle of the teeth 1314 of the rack 1312 may also bemodified to vary the resistance provided by the rack 1312 againstproximal translation of the proximal handle portion 1306. For example,each tooth 1314 may have a ramped tooth surface 1322 that forms an angle1325 relative to a longitudinal axis of the shaft 1308. The angle 1325may be increased or decreased to impart a corresponding change in theresistance provided by the rack 1312 to proximal translation of theproximal handle portion 1306. Although shown in FIG. 13 as having alinear ramped tooth surface 1322, in other implementations, each tooth1314 may instead have a contoured or curved profile to further vary theresistance profile provided as the proximal handle portion 1306 istranslated.

Referring to FIG. 13A, the rack 1312 may have a rack length 1320corresponding to a length of the shaft 1308 over which the rack 1312extends. In certain implementations, the rack length 1320 may be fromand including 0.08 inches to and including 1.25 inches. The rack 1312may also have a tooth density from and including 13.33 teeth per inch toand including 5 teeth per inch. Each of the teeth 1314 may have a toothheight 1321 from and including 0.02 inches to and including 0.07 inches.Each tooth may also have a ramped tooth surface 1322 forming an angle1325 from and including 10 degrees to and including 75 degrees relativeto a longitudinal axis 1324 of the shaft 1308.

FIGS. 14A-14B illustrate alternative implementations of tensioningassemblies in accordance with this disclosure, each of which may beimplemented in a retrieval system, such as the system 100 of FIG. 1D.

Referring first to FIG. 14A, a tensioning assembly 1400 a according toanother implementation is illustrated. Similar to the tensioningassembly 1300 of FIGS. 13A-13C, the tensioning assembly 1400 a includesa handle 1402 a including a distal handle portion 1404 a and a proximalhandle portion 1406 a having a shaft 1408 a that is disposed andtranslatable within the distal handle portion 1404 a. The shaft 1408 aincludes a rack 1412 a including a plurality of teeth 1414 a adapted toreceive a pair of pawls 1410 a, 1411 a coupled to the distal handleportion 1404 a. In contrast to the teeth 1314 of the rack 1312 of FIGS.13A-13C, which extended from the shaft 1308, the teeth 1414 a of therack 1412 a are formed into the shaft 1408 a and, as a result, extendinwardly from an exterior surface 1428 a of the shaft 1408 a,

As shown in FIG. 14A, the pawls 1410 a are coupled to mounting pins 1430a, 1431 a extending through the distal handle portion 1404 a. Each ofthe pawls 1410 a, 1411 a includes a button 1416 a, 1417 a that, whendepressed, causes rotation of the respective pawl 1410 a, 1411 a aboutthe mounting pins 1430 a, 1431 a. Each of the pawls 1410A, 1411 afurther includes a biasing member 1432 a, 1433 a adapted to bias thepawl 1410 a towards the shaft 1408 a. In the example implementation ofFIG. 14A, the biasing members 1432 a, 1433 a are in the form of sheetmetal springs, in other implementations, each biasing member 1432 a,1433 a may instead be, among other things, a torsion spring coiled abouta respective mounting pin 1430 a, 1431 a,

The shaft 1408 a may further define a retention groove 1434 a disposedproximal the rack 1420 a. The retention groove 1434 a may be positionedalong the shaft 1408 a such that the pawls 1410 a engage the retentiongroove 1434 a when the proximal handle portion 1406 a in a distal-mostposition, such as illustrated in FIG. 14A. The retention groove 1434 amay be shaped such that when engaged with the pawls 1410 a, 1411 aproximal movement of the proximal handle portion 1406 a relative to thedistal portion 1404 a is prevented or resisted. To disengage the pawls1410 a, 1411 a from the retention groove 1434 a, a user may simplydepress the buttons 1416 a, 1417 a to rotate the pawls 1410 a, 1411 aout of engagement with the retention groove 1434 a, thereby enablingunrestricted proximal movement of the proximal handle portion 1406 a.Although illustrated in FIG. 14A as being proximally displaced along theshaft relative to the rack 1402 a, the retention groove 1434 a mayinstead be a proximal tooth of the rack 1402 a provided the rack 1402 aextends sufficiently along the shaft 1408 a that the pawls 1410 a, 1411a engage the proximal tooth of the rack 1402 a when the proximal handleportion 1406 a is in a distal-most position.

Referring next to FIG. 14B, a tensioning assembly 1400 b according toyet another second implementation is illustrated. Similar to thetensioning assembly 1300 of FIGS. 13A-13C, the tensioning assembly 1400b includes a handle 1402 b including a distal handle portion 1404 b anda proximal handle portion 1406 b having a shaft 1408 b that is disposedand translatable within the distal handle portion 1404 b. The shaft 1408b includes a rack 1412 b including a plurality of teeth 1414 b adaptedto receive a pair of pawls 1410 b, 1411 b coupled to the distal handleportion 1404 b. In contrast to the pawls 1410 a, 1411 a of FIG. 14A,which extended in a proximal direction, the pawls 1410 b, 1411 b of FIG.14B extend in a distal direction. In either implementation, resistanceto distal movement of the proximal handle portion may be a result of oneor both of spring force exerted by biasing members and mechanicalinterference between the pawls and the rack.

In further contrast to the tensioning assembly 1400 a of FIG. 14A, thetensioning assembly 1400 b of FIG. 14B excludes a retention groove andinstead includes an elongated rack 1412 b including a proximal racksegment 1413 b shaped to receive the pawls 1410 b, 1411 b when theproximal handle portion 1406 b is disposed in a distal-most positionrelative to the distal handle portion 1404 b. As shown in FIG. 14B, thepawls 1410 b, 1411 b are coupled to mounting pins 1430 b, 1431 bextending through the distal handle portion 1404 b and each of the pawls1410 b, 1411 b includes a button 1416 b, 1417 b that, when depressed,causes rotation of the respective pawls 1410 b, 1411 b about themounting pins 1430 b, 1431 b, such rotation causing disengagement of thepawls 1410 b, 1411 b from the rack 1412 b. Each of the pawls 1410 b,1411 b further includes respective biasing members 1432 b, 1433 badapted to bias the pawls 1410 b, 1411 b towards the shaft 1408 b.

FIG. 15A is a top plan view of a first example biasing member 1500 andFIG. 15B is an isometric view of a second example biasing member 1550,each of which may be implemented as the biasing members 1432 a, 1433 aand 1432 b, 1433 b of FIGS. 14A and 14B, respectively. Each of theexample biasing members 1500, 1550 may be formed from sheet metal using,among other processes, laser cutting and stamping. The first examplebiasing member 1500 includes a coupling feature 1502 coupled to a loopedspring body 1504. Similarly, the second example biasing member 1550includes a coupling feature 1552 coupled to an elongated spring body1554 that terminates in a tab 1556. Each of the coupling features 1502,1552 is shaped to mate with or otherwise be retained by a correspondingfeature of the pawls shown in FIGS. 14A-14B. With reference to FIG. 14A,the spring bodies 1502, 1552 may extend from the buttons 1416 a, 1417 aof the pawls 1410 a, 1411 a and past the mounting pins 1430 a, 1431 asuch that the spring bodies 1502, 1552 abut or are otherwise retained byinternal features of the distal handle portion 1402 a.

The biasing force provided by the biasing members 1500, 1550 may bevaried by changing, among other things, the material, thickness, andoverall shape of the biasing members 1500, 1550. In certainimplementations, the biasing members 1500, 1550 may be formed from,among other things, steel and nitinol and may have a thickness from andincluding 0.004 inches to and including 0.022 inches.

FIG. 15C is a side elevation view of a third example of a biasing member1570 that may be implemented in the as the biasing members 1432 a, 1433a and 1432 b, 1433 b of FIGS. 14A and 14B, respectively. The biasingmember 1570 including a free leg 1572, a first loop 1574 and a secondloop 1576. In certain implementations, the biasing member 1570 may havea substantially square cross-section and be formed from a substantiallyresilient material such as, without limitation, 304V stainless steel.With reference to FIG. 14A, when installed, each of the first loop 1574and the second loop 1576 may be supported by respective pins extendingthrough the handle housing such that the free leg rests underneath andapplies an outward force on the buttons 1416 a, 1417 a. In certainimplementations, one of the pins may include one the mounting pins 1430a, 1431 a about which the pawls 1410 a, 1411 a rotate. Alternatively,one or both of the pins supporting the biasing member 1570 may beseparate from the mounting pins 1430 a, 1431 a.

D. Catheter Retrieval System Handle Including Counter-Rotation System

As previously discussed in the context of FIGS. 1A-8B, leadlesspacemakers may be fixed to the endocardium by a helical screw or similarfixation mechanism disposed on a distal end of the leadless pacemaker.As a result, fixation of the leadless pacemaker generally involvesrotating the leadless pacemaker in a first rotation direction such thatthe helical screw sufficiently penetrates and screws into theendocardium to maintain the leadless pacemaker in place. Subsequentretrieval and removal of the implanted leadless pacemaker generallyincludes coupling the leadless pacemaker to a catheter of a retrievalsystem and counter-rotating the leadless pacemaker to unscrew anddisengage the helical screw from the endocardium.

Rotation of the helical screw in the proper direction during each ofimplantation and retrieval of the leadless pacemaker is critical duringeach procedure. During implantation, for example, the helical screw willgenerally not engage the endocardium if rotated in the incorrectdirection. During retrieval, failure to rotate the leadless pacemaker inthe proper direction can be even more problematic. In addition tofailing to disengage the helical screw from the endocardium, rotation inthe fixation direction may drive the helical screw deeper into theendocardium and, in certain cases, may pierce through the endocardium orotherwise cause excessive trauma to the heart.

To address the foregoing issues, retrieval systems according to thepresent disclosure include a counter-rotation feature that prevents theuser from rotating a proximal handle portion in a predetermineddirection. In certain implementations, the counter-rotation feature isonly engaged after an implantable medical device is captured and dockedwith a retrieval catheter of the retrieval system. As a result, a usermay freely manipulate the proximal handle portion and a snare, tether,or similar retention mechanism coupled to the proximal handle portionduring initial capture of the implantable medical device whilesubsequently being protected from improper rotation following docking ofthe implantable medical device.

The counter-rotation feature disclosed herein increases safety ofcatheters while retrieving leadless pacemakers and other implantablemedical devices. The counter-rotation ensures correct rotation of aproximal handle portion of a retrieval system when the pacemaker isdocked such that the leadless pacemaker or similar implantable medicaldevice cannot be further rotated into tissue, such as the heart wall.The counter-rotation feature is only active while the leadless pacemakeror implantable medical device is docked to the retrieval system.Notably, the user is not generally required to perform additional stepsto activate or deactivate the counter-rotation feature. Rather, thecounter-rotation feature is engaged or disengaged automatically duringthe regular course of capturing and docking the implantable medicaldevice. In certain implementations, the counter-rotation feature mayalso produce an audible click or tactile bump every time the proximalhandle portion is rotated a predetermined number of degrees, therebyproviding additional information and feedback to the user duringunscrewing of the leadless pacemaker or other implantable medicaldevice.

FIG. 16A is a side view of a handle 1600 including a counter-rotationassembly 1601 for use in a retrieval system, such as the system 100illustrated in FIG. 1D. The handle 1600 generally includes a distalhandle portion 1604 and a proximal handle portion 1606. As illustratedin FIG. 14A, the proximal handle portion 1606 includes a shaft 1607 thatextends at least partially into the distal handle portion 1604. Theproximal handle portion 1606 is coupled to a tensioning member 1609,such as a wire, that extends from the handle 1602 and to a distal end ofthe retrieval system where the tensioning member 1609 may be coupled toor may terminate in a snare, tether, lasso, or similar retrieval featurethat may be coupled to a corresponding mating feature of an implantablemedical device, such as a leadless pacemaker.

Similar to the implementation previously described in the context ofFIGS. 13A-14B, the distal handle portion 1604 and the proximal handleportion 1606 may be coupled together by a ratchet mechanism 1608 thatincludes one or more pawls 1610 a, 1610 b of the distal handle portion1604 and a rack 1612 disposed on the shaft 1607. As described in moredetail in the context of FIGS. 13A-14B, the proximal handle portion 1606may be pulled and translated proximally to apply tension to thetensioning member 1609. As the proximal handle portion 1606 is furtherpulled in the proximal direction, the ratchet mechanism 1608 engagessuch that the proximal handle portion 1606 becomes “locked” relative tothe distal handle portion 1604. In the locked configuration, distalmovement of the proximal handle portion 1606 is prevented by engagementof the pawls 1610 a, 1610 b with the rack 1612 while further proximaltranslation of the proximal handler portion 1606 may be allowed toincrease tension on the tensioning member 1609.

The handle 1600 may be configured such that engagement of the ratchetmechanism 1608 corresponds to docking of the implantable medical devicewith a catheter of the retrieval system, such as described in thecontext of FIGS. 5A-6B. Accordingly, the initial tension applied by theproximal handle portion 1606 may coincide with operation of theretrieval feature (e.g., cinching or tightening of a snare) andsubsequent drawing together of the implantable medical device and thecatheter. When the implantable medical device and the catheter are incontact, as evidenced by engagement of the ratchet mechanism 1608, theimplantable medical device may be considered docked with respect to thecatheter and a user may sheath the implantable medical device with aguide catheter of the retrieval system. The proximal handle portion 1606may then be rotated counterclockwise to unfix the leadless pacemakerfrom the heart wall.

During retrieval of an implantable medical device, there is thepotential that a user of the retrieval system may incorrectly rotate theproximal handle portion 1606 in a clockwise direction resulting infurther screwing in of the implantable medical device into thecorresponding tissue. For example, clockwise rotation may cause thehelix of a leadless pacemaker to dig further into cardiac tissue. Toprevent such rotation, the handle 1600 includes anti-rotationfunctionality provided by interaction between a ratchet wheel 1650disposed on a distal end of the second handle portion 1606 and aprotrusion 1652 extending towards the shaft 1607 from the housing 1602.

In certain implementations, the protrusion 1652 and the ratchet wheel1650 are arranged with respect to each other such the ratchet wheel 1650is aligned with the protrusion 1652 when the proximal handle portion1606 is proximally translated into a position corresponding to dockingof an implantable medical device being retrieved. In implementationsincluding a ratchet mechanism, such as the ratchet mechanism 1608, sucha position may be signaled to the user by engagement of the ratchetmechanism 1608. The ratchet wheel 1650 is shaped such that when alignedwith the protrusion 1652, the protrusion 1652 substantially blocksrotation of the ratchet wheel 1650 in a clockwise direction, therebypreventing a user from rotating the proximal handle portion 1606 in aclockwise direction.

To disengage the anti-rotation functionality, a user may simply depressbuttons 1616 a, 1616 b or similar features adapted to release the pawls1610 a, 1610 b from the rack 1612. Once released, the proximal handlerportion 1606 may be translated distally to misalign the ratchet wheel1650 and the protrusion 1652, thereby allowing bi-directional rotationof the proximal handle portion 1606. Accordingly, in the event that auser must undock the leadless pacemaker from the retrieval catheter, theanti-rotation functionality is automatically disengaged withoutadditional intervention by the user.

FIG. 16B is an isometric view of the ratchet wheel 1650. In certainimplementations, the ratchet wheel 1650 may include two or more lobes1654, 1656 coupled to each other in an offset manner. By being offset,each lobe 1654, 1656 forms a respective stopping face 1658, 1660 thatabuts the protrusion 1652 when the ratchet wheel 1650 is aligned withthe protrusion 1652, as shown in FIG. 16C, and a clockwise rotation isapplied to the proximal handle portion 1606. In certain implementations,the ratchet wheel 1650 may be formed with the shaft 1607 or,alternatively, may be formed separately from the shaft 1607 and coupledto the shaft, such as by using ferrol or similar pins.

In the example of FIG. 16B, the ratchet wheel 1650 includes two offsetlobes 1654, 1656 having semi-circular shapes such that the ratchet wheel1650 provides a ratcheting effect every half rotation of the proximalhandler portion 1606. In other implementations, the quantity of lobesmay be increased such that a more discrete ratcheting effect isachieved. For example, in certain implementations, the ratchet wheel1650 may be composed of four offset quarter-circular lobes such thatratcheting is provided every quarter turn.

In addition to preventing clockwise rotation of the shaft 1607, theinteraction between the ratchet wheel 1650 and the protrusion 1652 alsoprovides audial and/or tactile feedback when the shaft 1607 is rotatedin the counterclockwise direction. Such feedback may be useful to a userof the handle 1600 to determine the number of counterclockwise rotationsthat have been applied to the proximal handle portion 1606 and, as aresult, a leadless pacemaker coupled to the retrieval catheter of theretrieval system.

Audial and/or tactile feedback is provided by interaction between theratchet wheel 1650 and the protrusion 1652 during counterclockwiserotation of the proximal handle portion 1607. In contrast to clockwiserotation during which the ratchet wheel is obstructed by the protrusion1652, counterclockwise rotation causes the protrusion 1652 to travelalong the outer surface of the lobes 1654, 1656, flex or deflecting theprotrusion 1652. In certain implementations, such deflection of theprotrusion 1652 may increase resistance to further counterclockwiserotation of the proximal handle portion 1606, thereby providing tactilefeedback to the user. Moreover, the outer surface of the lobes 1654,1656 may further be modified to produce a predetermined resistanceprofile. For example, the outer surface of the lobes 1654, 1656 asillustrated in FIGS. 16A-16C are semi-circular and, as a result,generally produce a resistance profile in which the resistance tocounterclockwise rotation increases gradually, peaks, and then decreasesgradually as the proximal handle portion 1606 is rotated. In anotherimplementation, the outer surface of the lobes 1654, 1656 may include alinear ramp such that the rotational resistance linearly increases asthe proximal handle portion 1606 is rotated.

As counterclockwise rotation is continued, the protrusion 1652 passesthe stopping faces 1658, 1660 of the lobes 1654, 1656. In certainimplementations, a click or other sound may occur along with a bump orsudden decrease in rotational resistance provided by the protrusion1652. During a retrieval process, a user may count the clicks and/orchanges in rotational resistance to track the number of counterclockwiserotations that have been applied to the proximal handle portion 1606.For example, the ratchet wheel 1650 would produce a click or bump everyhalf-turn.

In addition to varying the quantity and shape of the ratchet wheel 1650,performance characteristics of the handle 1600 may further be modifiedby varying the design of the protrusion 1652. FIG. 17A illustrates theprotrusion 1652 of the handle 1600 in further detail. As shown, theprotrusion 1652 is a multi-part fin 1652 extending from an internalsurface of the housing 1602. More specifically, the multi-part fin 1652includes a base 1670 from which three fin segments 1672 a, 1672 b, 1672c extend.

Each of the fin segments 1672 a-1672 c may be positioned such that thedistal shaft end 1650 aligns with one or more of the fin segments 1672a-1672 c as the distal shaft end 1650 is moved between different lockedpositions. The fin segments 1672 a-1672 c are generally spaced such thatthe distal shaft end 1650 is unable to be rotated between any twoadjacent pairs of the fins segments 1672 a-1672 c.

The size, shape, and construction of the protrusion 1652 may be modifiedto change the resistance provided by the protrusion 1652 tocounterclockwise rotation of the proximal handle portion 1606. Forexample, the length the fin segments 1672 a-1672 c may be increased orthe thickness of the fin segments 1672 a-1672 c may be decreased inorder to reduce the rigidity of the fin segments 1672 a-1672 c and, as aresult, reduce the resistance provided by the fine segments 1672 a-1672c to counterclockwise rotation of the proximal handle portion 1606.Conversely, the length of the fin segments 1672 a-1672 c may beshortened or the thickness of the fin segments 1672 a-1672 c may beincreased to increase the rigidity of the fin segments 1672 a-1672 c.The material used for the fin segments 1672 a-1672 c may also beselected to impart specific rigidity to the fin segments 1672 a-1672 c.

In other implementations, more or fewer fin segments may be implemented.For example, FIG. 17B illustrates a one-piece fin 1752 extending fromthe housing 1602.

FIG. 18A is an isometric view of an alternative shaft 1807 that may beimplemented as part of the proximal handle portion 1606 of the handle1600. FIG. 18B is a cross sectional view of the handle 1600 includingthe shaft 1807.

Similar to the shaft 1607 illustrated in FIG. 16A, the shaft 1807includes a rack 1812 adapted to engage corresponding pawls 1610 of adistal handle portion 1604 (each shown in FIG. 16A) into which the shaft1807 is inserted. In particular, the rack 1812 includes a plurality ofteeth 1814 shaped to engage the pawls 1610 to restrict distal movementof the proximal handle portion 1606 while still enabling furtherproximal movement of the proximal handle portion 1606. Between adjacentpairs of teeth 1814 of the rack 1812, secondary teeth 1816 are disposedabout the circumference of the shaft 1807. The secondary teeth 1816 areshaped and positioned to block clockwise rotation of the shaft 1807 whenthe pawls 1610 a, 1610 b have engaged the rack 1812. Accordingly, eachof the sections disposed between adjacent teeth 1814 of the rack definesan independent ratchet wheel adapted to allow rotation of the shaft 1807in a first direction while obstructing rotation of the shaft 1807 in asecond direction opposite the first direction as determined by the shapeand orientation of the secondary teeth 1816.

Referring to FIG. 18B the anti-rotation functionality provided by thesecondary teeth 1816 is further illustrated. FIG. 18B is a simplifiedcross-sectional view of the handle 1600 including the alternative shaft1807 in taken in a distal direction. The distal handle portion 1604 isshown with the pawls 1610 a, 1610 b engaging a tooth 1814 of the rack1812 formed into the surface of the shaft 1807. As previously noted, aplurality of secondary teeth 1816 are circumferentially distributedabout the shaft 1807 between adjacent teeth 1814 of the rack 1812.

Each of the secondary teeth 1816 generally includes a ramped toothsurface 1818 and a stopping face 1820. The ramped tooth surfaces 1818 ofthe secondary teeth 1816 are oriented such that counterclockwiserotation of the shaft 1807 causes the pawls 1610 to ride over thesecondary teeth 1816. In contrast, the stopping faces 1820 are orientedsuch that clockwise rotation of the shaft 1807 causes the pawls 1610 toabut the stopping faces 1820, thereby preventing further clockwiserotation of the shaft 1807.

Similar to the interaction between the distal shaft end 1650 and theprotrusion 1652, interaction between the secondary teeth 1816 and thepawls 1610A, 1610B may result in one or both of audial and tactilefeedback. As the shaft 1807 is rotated in a clockwise direction and thepawls ride over the secondary teeth 1816, interference between thesecondary teeth 1816 and the pawls 1610, 1610B may result in anincreased resistance to clockwise rotation of the shaft 1807. When thesecondary teeth 1816 are overcome by further rotation of the shaft 1807,a corresponding bump or click may result as the interference between thepawls 1610A, 1610B and the secondary teeth 1816 is eliminated. Althoughillustrated in FIG. 18B as being substantially linear, the ramped toothsurfaces 1818 may have other shapes selected to provide a specificrotational resistance profile as the pawls 1610A, 1610B are passed overthe secondary teeth 1816. For example, the ramped tooth surfaces 1818may be curved or include multiple sections having different ramp angles.

The quantity and distribution of the secondary teeth 1816 may also bevaried to provide finer or more granular feedback to a user of thehandle 1600 and to limit the amount of clockwise rotation permitted bythe handle 1600. For example, the shaft 1807 of FIG. 18B includes foursecondary teeth 1816, thereby providing a bump or click in response toevery quarter turn of the shaft 1807 and limiting clockwise rotation tono more than a quarter turn of the shaft 1807. In certainimplementations, additional secondary teeth 1816 may be included toprovide more frequent feedback and to further limit the amount ofpermissible rotation in the clockwise direction. Similarly, fewersecondary teeth 1816 may be included to provide less frequent feedbackand to enable a larger amount of clockwise rotation.

E. Catheter Delivery System Handle Including Torsional Strain ReliefSystem

Conventional retrieval systems for implantable medical devices, such asleadless pacemakers, include a snare or similar retrieval feature thatis adapted to couple with a button or similar feature of the leadlesspacemaker. In the case of a snare, tension may then be applied to thesnare to close or cinch the snare about the coupling feature of theleadless pacemaker and to dock the leadless pacemaker within a dockingcap or similar structure disposed on a distal end of a retrievalcatheter of the retrieval system.

Once docked, the leadless pacemaker may be unscrewed from tissue inwhich the leadless pacemaker is implanted by applying torque to a torqueshaft that is coupled to the retrieval catheter by a drive gear. Inconventional retrieval systems, transmission of torque from a handle ofthe retrieval system to the leadless pacemaker requires that the drivegear of the torque shaft properly seat in and engage the docking cap. Ifthe drive gear does not engage the docking cap, torque is nottransmitted through the torque shaft as intended, but is insteadtransmitted through the snare. Buildup of torque in the snare can leadto several unwanted events. For example, the snare may be permanentlydamaged or fracture such that the snare is unable to function properlyor the snare may cause the coupling feature of the pacemaker to bedamaged.

In light of the foregoing, the present disclosure provides a handle fora retrieval system for use in retrieving leadless pacemakers and similarimplantable medical devices that includes a torsion release mechanism.The torsion release mechanism rotationally decouples the retrievalfeature from the retrieval catheter once the leadless pacemaker or otherimplantable medical device is properly docked. Prior to docking, theretrieval feature is rotationally coupled to the handle to enable a userto position the retrieval feature by making rotational adjustments tothe handle. However after docking, the retrieval feature is allowed tounwind and release built up torsional energy. Accordingly, the mechanismdisclosed herein allows for positioning of the retrieval feature priorto docking and allows for relief of torsional buildup on the retrievalfeature snare without losing tension on the implantable medical device.

The torsional strain relief mechanism of the present disclosuregenerally includes a handle within which a first gear is rotationallysupported, for example, by a ball bearing. The first gear is coupled tothe retrieval feature such that rotation of the first gear causesrotation of the retrieval feature. The torsional strain relief mechanismfurther includes a shuttle having a second gear. The shuttle isrotationally fixed to the handle but is translatable along the handlebetween a first shuttle position and a second shuttle position. In thefirst shuttle position the first gear and the second gear are engagedsuch that rotation of the handle causes rotation of the retrievalfeature, in the second shuttle position, the first gear and the secondgear are disengaged. When disengaged, the first gear is able to rotatefreely within the housing because of the rotational mounting of thefirst gear to the housing. As a result, the first gear can spin tounwind the retrieval feature and dissipate any torsion that may be builtup on the retrieval feature. Any further rotation of the handle when thefirst and second gears are disengaged results in rotation of therotational mount about the first gear without generating torsion on theretrieval feature.

FIGS. 19A-19B are cross-sectional side view of a handle 1900 inaccordance with the present disclosure. The handle 1900 generallyincludes a housing 1901 and a torsion release assembly 1902 including afirst gear 1903 supported by a rotational mount 1904 that is furthersupported within the housing 1901. The first gear 1903 is fixed to asnare 1910 or similar retrieval feature such that rotation of the firstgear 1903 results in rotation of the snare 1910. The handle 1900 furtherincludes a shuttle assembly 1906 that is rotationally fixed to thehousing 1901 and includes a second gear 1908. As shown in the transitionbetween FIGS. 19A and 19B, the shuttle assembly 1906 is translatablealong the housing 1901 between a first shuttle position (shown in FIG.19A), which generally corresponds to a proximal position of the shuttleassembly 1906, and a second shuttle position (shown in FIG. 19B), whichgenerally corresponds to a distal position of the shuttle assembly 1906.Also, as illustrated in FIG. 19B, in certain implementations the snare1910 may extend through the shuttle assembly 1906 to be coupled to thefirst gear 1903.

The snare 1910 may generally be disposed within a catheter shaft 1911coupled to the shuttle assembly 1906. Accordingly, as the shuttleassembly 1906 is translated between the first shuttle position and thesecond shuttle position, the catheter shaft 1911 similarly translates.As a result of such translation of the catheter shaft 1911, the snare1910 may be drawn into the catheter shaft 1911 such that the snare 1910is cinched. Such cinching may be used, for example, to capture anattachment feature 1915 of a leafless pacemaker 1913 or otherimplantable medical device with the snare 1910, as shown in FIG. 19B.

Referring first to FIG. 19A, when in the first shuttle position, thefirst gear 1903 and the second gear 1908 engage each other. Because thesecond gear 1908 is coupled to the shuttle assembly 1906 which is inturn rotationally fixed relative to the housing 1901, engagement of thefirst gear 1903 to the second gear 1908 results in the first gear 1903being similarly rotationally fixed relative to the housing 1901.Accordingly, rotation of the handle 1900 when the shuttle assembly 1906is in the first shuttle position results in rotation of each of theshuttle assembly 1906, the second gear 1908, the first gear 1903, andthe snare 1910.

In contrast, FIG. 19B illustrates the shuttle assembly 1906 in thesecond shuttle position in which the second gear 1908 is disengaged fromthe first gear 1903. When disengaged from the second gear 1908, thefirst gear 1903 may freely rotate relative to the housing 1901 by virtueof the rotational mount 1904. For example, in implementations in whichthe rotational mount 1904 is a ball bearing including an inner race andan outer race, the outer race may be coupled to the housing 1901 whilethe inner race may be coupled to the first gear 1903. Accordingly, thehousing 1901 and the first gear 1903 may rotate independently of eachother absent any additional coupling of the first gear 1903 to thehousing 1901.

During operation, a user may initiate capture of a leadless pacemakerwith the shuttle assembly 1906 disposed in the first shuttle position,thereby allowing the user to rotate and manipulate the snare 1910 byrotating the handle 1900 to facilitate capture of the leadlesspacemaker. Subsequent docking of the leadless pacemaker may be achievedby translating a torque shaft over a distal end of the snare 1910 suchthat the snare 1910 is cinched or otherwise tightened. In certainimplementations, the shuttle assembly 1906 may be coupled to the torqueshaft of the retrieval system such that distal translation of theshuttle assembly 1906 translates the torque shaft over the distal end ofthe snare 1910.

In addition to translating the torque shaft over the snare 1910, distaltranslation of the shuttle assembly 1906 disengages the first gear 1903from the second gear 1908, allowing the first gear 1903 to freely rotatewithin the housing 1901. To the extent that any torsion had been builtup in the snare 1910 during the capture and docking processes, suchtorsion is relieved by free rotation of the first gear 1903 within therotational mount 1904 counter to the direction of the torsion. With thefirst gear 1903 free to rotate within the rotational mount 1904, anysubsequent rotation of the handle 1901 with the shuttle assembly 1906 inthe second shuttle position does not result in additional torsion beingapplied to the snare 1910. As a result, inadvertent over-torsion of thesnare 1910 is avoided.

In certain implementations, the shuttle assembly 1906 is configured totranslate over a one inch travel range relative to the housing 1901. Insuch implementations, the first shuttle position in which the first gear1903 is engaged with the second gear 1908 may correspond to the shuttleassembly 1906 being disposed within the proximal three-quarters of aninch of the travel range. Conversely, the second shuttle position inwhich the first gear 1903 is disengaged from the second gear 1908 maycorrespond to the distal one-quarter inch of the travel range.

As previously noted, the rotational mount 1904 supports the torsionrelease assembly 1902 within the housing 1901 such that the first gear1903 is freely rotatable within the housing 1901 absent engagement withthe second gear 1908. In certain implementations, the rotational mount1904 may be a bearing including ball, roller, or similar rollingelements. Tension on the snare 1910 during use of the handle 1900 toretrieve a leadless pacemaker or similar implantable medical devicegenerally results in the torsion release assembly 1902 being pulled in adistal direction. To resist such forces, the rotational mount 1904 maybe selected to include roller elements having high compressive strength,such as ball bearings made of steel or other metals.

FIG. 20A is an isometric view of the shuttle assembly 1906 and thesecond gear 1908. As shown, the shuttle assembly 1906 may include ashuttle body 1912 from which grip features 1914 a, 1914 b extend. Thegrip features 1914 a, 1914 b extend through the housing 1901 (as shownin FIGS. 19A-19B) such that a user may push or pull the grip features1914 a, 1914 b or structural features of the handle 1900 in contact withthe grip features 1914 a, 1914 b to translate the shuttle assembly 1906within the housing 1901. To improve moldability and manufacturing of theshuttle assembly 1906, the shuttle assembly 1906 and second gear 1908may be formed from two shuttle assembly halves 1907 a, 1907 b that arecoupled together.

FIG. 20B is an isometric view of the torsion release assembly 1902. Asillustrated, the first gear 1903 generally includes a gear shaft 1916coupled to a gear hub 1918, the gear hub 1918 being adapted to bereceived within the rotational mount 1904 (shown in FIG. 19A-B). Asshown in FIGS. 20A and 20B, each of the first gear 1908 and the secondgear 1902 are substantially square in shape. Similar to the shuttleassembly 1906, in certain implementations, moldability and manufacturingof the shuttle torsion release assembly 1902 may be improved by formingthe torsion release assembly from two torsion release assembly halves1905 a, 1905 b that are subsequently coupled together.

FIGS. 20C and 20D are side views of the shuttle assembly 1906 and thesecond gear 1908 in a disengaged and engaged configuration,respectively. When engaged, as in FIG. 20D, the first gear 1903 isinserted into the second gear 1908, thereby coupling the first gear 1903to the shuttle assembly 1906.

FIGS. 20C and 20D illustrate engagement of the first gear 1903 and thesecond gear 1908 when the first gear 1903 and the second gear 1908 areoriented such that the first feat 1902 is properly aligned with thesecond gear 1908. Such orientation is likely to be rare during actualuse and, as a result, the second gear 1908 may include self-aligningfunctionality adapted to rotate the first gear 1903 into the dockingorientation. For example, in certain implementations, the second gearmay include proximal guide surfaces that rotate the first gear 1903 intoproper engagement orientation.

FIG. 20E is a side view of the proximal end of the second gear 1908 andillustrates such guide surfaces. As shown in FIG. 20E, the second gear1908 may define a longitudinal axis 1919 extending along the second gear1908 normal to a cross-sectional plane 1921. The second gear 1908 mayfurther include a first half 1920 having a first guide surface 1922defining a first plane 1923 and a second half 1924 having a second guidesurface 1926 defining a second plane 1927. The first plane 1923 isoriented at a first angle 1930 relative to the cross-sectional plane1921 while the second plane 1927 is oriented at a second angle 1932relative to the cross-sectional plane 1921 that is supplementary to thefirst angle 1926. As a result, the first and second planes 1923, 1927intersect along a line 1929 (extending into the page of FIG. 20E) thatis perpendicular to the longitudinal axis 1919. In certainimplementations, the first angle 1930 may be from and including 35degrees to and including 55 degrees.

FIGS. 20F-20H are isometric views of the shuttle assembly 1906 and thefirst gear 1903 during alignment and engagement of the first gear 1903and the second gear 1908 when the first gear 1903 and the second gear1908 are initially out of alignment. Referring first to FIG. 20F, theshuttle assembly 1906 is translated proximally towards the first gear1903. Next, as shown in FIG. 20G, the proximal end of the second gear1908 meets the distal end of the first gear 1903 and the guide surfaces1922, 1926 contact the distal end of the first gear 1903. As the shuttleassembly 1906 is further translated, the first gear 1903 is rotated intoproper orientation. Once in proper alignment, further translation of theshuttle assembly 1906 results in insertion of the first gear 1903 intothe second gear 1906 and engagement of the first gear 1903 with thesecond gear 1908, as shown in FIG. 20H.

FIG. 21 is an isometric view of an alternative embodiment of a handle2100 according to the present disclosure. The handle 2100 includes ahousing 2101 that is partially removed. Similar to the handle 1900illustrated in FIGS. 19A-20H, the handle 2100 includes a torsion releaseassembly 2102 including a first gear 2103 supported by a rotationalmount 2104, such as a ball bearing. The first gear 2103 is coupled to asnare 2110 or similar retrieval feature such that rotation of the firstgear 2103 results in rotation of the snare 2110. The handle 2100 furtherincludes a shuttle assembly 2106 that is rotationally fixed to thehousing 2101 and that includes a second gear 2108. The shuttle assembly2106 is translatable along the housing 2101 between a first shuttleposition in which the first gear 2103 is disengaged from the second gear2108 and a second shuttle position in which the first gear 2103 isengaged with the second gear 2108.

Engagement between the first gear 2103 and the second gear 2108 isachieved by corresponding splines extending longitudinally along each ofthe first gear 2103 and the second gear 2108. As illustrated in FIG. 21,for example, the first gear 2103 may include a first gear shaft 2150 andmultiple first splines, such as first spline 2152, arrangedcircumferentially about the first gear shaft 2150. The second gear 2108includes a tubular body 2154 defining a channel into which the firstgear shaft 2150 is inserted when the shuttle 2106 is disposed in thesecond shuttle position. The second gear 2108 further includes at leastone second spline 2156 extending inwardly from the tubular body 2154such that as the first gear shaft 2150 is inserted into the tubular body2154, the second spline 2156 is inserted between an adjacent pair of thefirst splines 2152. As a result, the first gear 2103 and the second gear2108 become rotationally coupled and subsequent rotation of the handle2100 rotates the snare 2110.

F. Docking Cap for Leadless Pacemaker Retrieval

As previously described in the context of FIGS. 4A-4G, retrieval of aleadless pacemaker or similar implantable medical device generallyincludes coupling the leadless pacemaker and docking the leadlesspacemaker to a docking cap. To do so, a snare, tether, lasso, or similarretrieval feature mechanism is extended from a retrieval catheter andcoupled to an attachment feature, such as an attachment button, of theleadless pacemaker. Once coupled, the retrieval feature is proximallyretracted, thereby docking the leadless pacemaker within the dockingcap.

With conventional leadless pacemakers and retrieval systems, theforegoing capture and docking process generally requires that theleadless pacemaker and docking cap be substantially aligned as theleadless pacemaker is drawn into the docking cap. If such alignment doesnot occur, interference between the attachment feature and the dockingcap may occur, preventing complete docking of the leadless pacemaker.For example, as illustrated in FIG. 22A, the retention feature 424 mayinterfere with a leading edge of the docking cap 418 or, as illustratedin FIG. 22B, the retention feature 424 may enter the docking cap 418 atan angle such that the retention feature 424 obstructs entry of theleadless pacemaker 402 into the docking cap 418. Accordingly, ifalignment between the leadless pacemaker 402 and the docking cap 418 isnot sufficient, a failed docking interface may result which necessitatesanother docking attempt. In certain conventional systems, an acute anglebetween the leadless pacemaker 402 and the docking cap 418 maybe avoidedby applying tension to the leadless pacemaker 420 following capture andprior to docking. However, applying such tension risks damage to thetissue in which the leadless pacemaker 402 is implanted and undue strainon the snare and retention feature 424 which may lead to breakage ofeither the snare or the retention feature 424. Repeated docking andtension on the system may also induce additional stress on the heartwall during the retrieval procedure.

In light of the foregoing, the current disclosure is directed to adocking cap having improved docking and, in particular, a docking capthat reduces the degree of alignment required between the docking capand proximal end of the leadless pacemaker for successful docking.

The docking cap disclosed herein includes various features directed toimproved docking between the docking cap and a leadless pacemaker orsimilar implantable medical device. In contrast to the edge ofconventional docking cap designs, the docking cap includes a profileddistal end that guides a retention feature of a leadless pacemaker intothe internal volume defined by the docking cap. Once the retentionfeature is disposed within the internal volume, interference between theretention feature and the docking cap is reduced by cutouts or openingsdisposed about the docking cap. Such cutouts enable the retentionfeature to travel outside the internal volume of the docking cap duringdocking, reducing the likelihood that the retention feature will becomejammed within the docking cap and prevent docking of the leadlesspacemaker. In certain implementations, a flexible sheath is disposedabout the openings such that the retention feature is able to traveloutside the envelope of the docking cap, but the sheath maintains aninward force on the retention feature such that the retention feature isbiased towards the internal docking cap volume. By doing so, thelikelihood that the retention feature will become lodged or otherwiseinterfere with structural features of the docking cap is reduced.

FIGS. 22C and 22D are isometric views of a docking cap 2200 inaccordance with the present disclosure. FIG. 22E is a bottom view of thedocking cap 2200. In general, the docking cap 2200 forms a cage-likestructure defining an internal docking cap volume 2210 adapted toreceive the proximal end of a leadless pacemaker or similar implantablemedical device. The docking cap 2200 includes a proximal cap end 2202adapted to be coupled to the retrieval catheter shaft and a distalannulus 2204 disposed opposite the proximal cap end 2202. As shown inFIG. 22E, the proximal cap end 2202 may define a receptacle 2212 shapedto receive a drive gear during retrieval of the leadless pacemaker. Incertain implementations, the docking cap 2200 may be formed using atleast one of stainless steel (such as 304 stainless steel), titanium,and a polymer, such as polyether ether ketone (PEEK). In certainimplementations, the material used to form the docking cap 2200 may beloaded with a radiopaque additive or otherwise visible using fluoroscopyor a similar imaging technique.

As shown in FIG. 22E, the internal docking cap volume 2210 may have aninternal diameter 2211. In certain implementations, the internaldiameter may be from and including 0.200 inches to and including 0.250inches and may be depend on the size of the introducer or catheter towhich the docking cap 2200 is coupled. In conventional docking caps,docking of the leadless pacemaker and its retention feature is generallylimited by the internal diameter 2211 of the internal docking cap volume2210. However, referring back to FIGS. 22C-D, docking caps according tothe present disclosure include longitudinal members 2206 extendingbetween the proximal cap end 2202 and the distal annulus 2204 to defineopenings, such as opening 2208, between adjacent longitudinal members2206. The openings 2208 are sufficiently sized to allow the proximal endof a leadless pacemaker and, in particular, the coupling featuredisposed at the proximal end of the leadless pacemaker to pass at leastpartially through the openings 2208 during the capture and retrievalprocesses, thereby expanding the effective diameter of the docking capbeyond the internal diameter 2211.

To accommodate the proximal end of the leadless pacemaker and/or thecoupling feature of the leadless pacemaker, the longitudinal members2206 are generally disposed about the docking cap 2200 such that theminimum distance between adjacent longitudinal members 2206 is greaterthan the width of the proximal end of the leadless pacemaker and/or thecoupling feature of the leadless pacemaker. Accordingly, whileillustrated in FIGS. 22C-22E as including three longitudinal members2206 and three corresponding openings defined between the longitudinalmembers, other docking caps in accordance with this disclosure may havemore or fewer longitudinal members 2206 and corresponding openingsprovided they can accommodate the leadless pacemaker of the particularapplication.

In certain implementations, a torque transmission feature 2214 may becoupled to one of the longitudinal members 2206 and extend into thedocking cap volume 2210. The torque transmission feature 2214 ispositioned and shaped such that after docking of the leadless pacemaker,rotation of the docking cap 2200 causes the torque transmission feature2214 to contact the docked leadless pacemaker and transmit torque fromthe docking cap 2200 to the leadless pacemaker such that the leadlesspacemaker may be unscrewed from tissue.

FIGS. 22F and 22G are a side view and a cross-sectional side view,respectively of the docking cap 2200. As shown in FIGS. 22F-22G, thedocking cap 2200 may include a sheath 2216 disposed over a portion ofthe docking cap 2200 including the openings 2208. The sheath 2216 isgenerally formed from an elastic material. By doing so, the sheath 2216allows the retention feature of a leadless pacemaker to extend throughthe openings 2208 while maintaining inward pressure that biases theretention feature into the internal docking cap volume 2210. As a resultof the inward biasing provided by the sheath 2216, the retention featureis directed away from edges and other features of the docking cap 2200on which the retention feature may become bound up. In addition toassisting during docking of a leadless pacemaker, the inward forceprovided by the sheath 2216 on the retention feature also facilitatesalignment of the retention feature with the distal annulus 2204 shouldundocking of the leadless pacemaker be required.

In certain implementations, the sheath 2216 may be formed from one ormore of a copolymer, polytetrafluoroethylene (PTFE), and perfluoroalkoxyalkane (PFA) and may have a thickness from and including 0.006 inches toand including 0.020 inches. For example, in one implementation, thesheath 2216 is formed from a fluorinated ethylene propylene (FEP) sheethaving a thickness of 0.012 inches that is applied to the docking cap2200 by heat shrinking the FEP sheet onto the outside surface of thedocking cap 2200.

FIG. 22H is a detailed view of the distal annulus 2204 of the dockingcap 2200. In certain implementations, to facilitate entry of animplantable medical device, such as a leadless pacemaker, into thedocking cap 2200 during the docking process, the distal portion of thedistal annulus 2204 may be shaped to reduce edges on which theimplantable medical device may become caught. For example, in certainimplementations, the distal annulus 2204 may include a distal face 2220and an internal surface 2222 substantially perpendicular to the distalface 2220. A curved transition 2224 may extend between the distal face2220 and the internal surface 2222 to guide a captured implantable leadinto the docking cap 2200 during the docking process. In certainimplementations, the curved transition may have a radius of curvature2226 from and including 0.017 inches to and including 0.150 inches andan arc length 2228 from and including 0.017 inches to and including0.035 inches.

To further reduce the likelihood of the leadless pacemaker becomingcaught at or near the distal annulus 2204, the torque feature 2214 mayalso be offset from the distal face 2220 of the distal annulus 2204. Forexample, the torque feature 2214 may originate from a proximal edge ofthe curved transition 2224 and include a concave scallop 2232 thatterminates in a longitudinal face 2234. Accordingly, in certainimplementations, the longitudinal face 2234 may have an offset 2230 fromand including 0.065 inches to and including 0.120 inches relative to thedistal face 2220.

G. Self-Aligning Drive Gear Assembly for Leadless Pacemaker Retrieval

As previously discussed in the context of FIGS. 4A-6B, retrieval of aleadless pacemaker or similar implantable medical device may beaccomplished by snaring or otherwise capturing an attachment feature,such as a button, on the proximal end of the leadless pacemaker with aretrieval catheter, retracting the pacemaker into a docking cap, andunscrewing the pacemaker from the cardiac tissue.

Transmission of torque from the handle of the retrieval system to thedocked pacemaker may be accomplished by a drive gear disposed on adistal end of the retrieval catheter or other torque shaft. Morespecifically, as the retrieval catheter or torque shaft is retractedduring docking of the leadless pacemaker, the drive gear seats orotherwise engages with a corresponding feature of the docking cap. Oncemated, rotation of the drive gear causes rotation of the docking cap,which transfers torque to unscrew the leadless pacemaker. Notably, ifthe drive gear does not properly engage with the docking cap, torque isnot transmitted through the torque shaft as intended, but through thesnare or other retrieval feature. Buildup of torque in the snare canlead to several unwanted events. For example, the snare may bepermanently damaged and not function correctly, the snare couldfracture, or the snare could cause the attachment feature of thepacemaker to detach and become embolic.

Conventional drive gear and docking cap arrangements require a precisefit and a specific orientation to mate and deliver torque. Due totension in the torque cable and the geometry of the legacy componentsduring docking, the drive gear does not self-align inside the dockingcap recess if it is not correctly seated initially. Subsequently, thetorque performance of the retrieval catheter suffers.

In light of the foregoing, the present disclosure is directed to adocking cap and drive gear design with improved seating and interfacingbetween the docking cap and drive gear. As a result, drive gears anddocking caps in accordance with the present disclosure provide moreorientation options that still result in proper mating between thecomponents and allow the drive gear to self-align and seat within thedocking cap if perfect mating orientation is not initially achieved.

The drive gear and docking cap have been designed with geometry thatencourages seating of the drive gear within the docking cap.Additionally, the interface between the drive gear and docking capincludes a limited number of interference points, thereby allowing moreorientations for proper seating and fewer opportunities for interferencewhich forfeits torque performance. Moreover, if the drive gear isinitially drawn into the docking cap in an orientation that interfereswith proper seating of the drive gear or in which the drive gear doesnot fully engage the docking cap, the drive gear self-aligns aftertorque is applied such that the drive gear seats within the docking capand torque transfer performance is maintained.

The docking cap geometry has been designed to work in tandem with thedrive gear to facilitate self-alignment between the components. Thedocking cap recess, which receives the drive gear, is generally deepenough to maintain and transmit torque should an interferenceconfiguration be achieved. Also, at least a portion of the recess isshaped to avoid interference with the drive gear after the drive gearhas been retracted into the docking cap. As a result, the drive gear maybe rotated within the recess to facilitate self-alignment.

FIGS. 23A-23E illustrate general operation of a docking system 2300 inaccordance with the present disclosure. The docking system 2300 includesa drive gear 2302 disposed on the end of a torque shaft 2304 orretrieval catheter. The torque shaft 2304 extends through a docking cap2306 and is translatable relative to the docking cap 2306. As previouslydiscussed in the context of FIGS. 4A-6B, the docking cap 2306 may bedisposed at a distal end of a catheter shaft and, in certainimplementations, may be coupled to the distal end of the catheter shaftusing a rotatable coupling such that the docking cap 2306 is able torotate relative to the catheter shaft. The docking cap 2306 may, butdoes not necessarily include the various docking cap features previouslydiscussed in the context of FIGS. 22C-H.

A retrieval feature 2308 (shown in FIG. 23A in dashed lines for clarity)generally extends through the torque shaft 2304 such that the retrievalfeature may be used to capture a corresponding attachment feature of aleadless pacemaker or other implantable medical device. To facilitatesuch capture, the torque shaft 2304 may be extended from the docking capas illustrated in FIG. 23A.

As shown in FIGS. 23B, following capture of the leadless pacemaker, thetorque shaft 2304 is retracted into the docking cap 2306 to dock theleadless pacemaker. FIG. 23C illustrates the torque shaft 2304 in afully retracted position such that the drive gear 2302 is retainedwithin a recess 2310 defined within the docking cap 2306.

As shown in FIG. 23D, the recess 2310 may, in certain implementations,be substantially rectangular in shape such that the recess 2310 isdefined by a first pair of long opposing walls 2312 a, 2312 b arrangedperpendicular to each of a second pair of shorter opposing walls 2314 a,2314 b. The dimensions and spacing of the first pair of opposing walls2312 a, 2312 b and the second pair of opposing walls 2314 a, 2314 b isgenerally dependent on the size and shape of the drive gear 2302 inorder to facilitate self-alignment of the drive gear 2302 and thedocking cap 2306. As illustrated by the arrangement of FIG. 230, thedrive gear 2302 may be retracted into the recess 2310 in an orientationin which the drive gear 2302 does not interfere with the docking cap2306. However, as illustrated in FIG. 23E, the drive gear 2302 may berotated relative to the docking cap 2306 such that the drive gear 2302interferes with the first pair of opposing walls 2312A, 2312B, therebyenabling torque transfer from the torque shaft 2304 to the docking cap2306. As a result, the drive gear 2302 may be retracted into the recess2310 of the docking cap 2306 in any orientation relative to the dockingcap 2304 and may become properly seated for torque transfer by simplyrotating the torque shaft 2304 and the drive gear 2302.

Once seated, further rotation of the drive gear 2302 by rotation of thetorque shaft 2304 results in rotation of the docking cap 2306. Suchfurther rotation may be used to unscrew a leadless pacemaker or otherimplantable medical device from tissue or perform other functions. Incertain implementations, the drive gear 2302 may be adapted to bedisengaged from the docking cap 2306 by rotating the drive gear 2302 ina direction opposite that used to engage the drive gear 2302 and thedocking cap 2306. More specifically, counter-rotation of the drive gear2302 within the docking cap 2306 may eliminate the interference betweenthe drive gear 2302 and the docking cap 2306 such that the drive gear2302 may be distally extended from the docking cap 2306 or otherwisemoved independently from the docking cap 2306.

In the example implementation of FIGS. 23A-23E, the drive gear 2302 andrecess 2310 are shaped such that interference occurs between each of thefirst pair of opposing walls 2312A, 2312B and opposite corners 2316A,2316B (shown in FIG. 23E) of the drive gear 2302. Accordingly, theopposite corners 2316A, 2316B function as torque features of the drivegear 2302 adapted to engage corresponding recess torque features (here,the first pair of opposing walls 2312A, 2312B) of the docking cap 2306to transfer torque from the torque shaft 2304 to the docking cap 2306.To achieve this result, each of the first pair of opposing walls 2312A,2312B have a length that is greater than the maximum width of the drivegear 2302 (which, in the current example is a diagonal distance 2318between the opposite corners 2316A, 2316B) and each of the second pairof opposing walls 2314A, 2314B has a length that is less than themaximum width of the drive gear 2302.

As shown in FIG. 23E, the recess 2310 may also have a lip 2320 thattransitions from a first perimeter 2322 having short sides that exceedthe maximum width of the drive gear 2302 to a second perimeter 2324defined by the second pair of opposing walls 2314 a, 2314 b. As aresult, the lip 2320 further guides the drive gear 2302 into the recess2310 such that proper alignment occurs between the drive gear 2302 andthe docking cap 2306. As illustrated in FIG. 23C, the drive gear 2302may be shaped to at least partially extend beyond the lip 2320 when thedrive gear 2302 is received within the recess 2306.

FIG. 24 and FIG. 25 are isometric views of the drive gear 2302 and thedocking cap 2306 of the docking system 2300, respectively. Asillustrated in FIG. 24, the drive gear 2302 includes a distal portion2330 including a cuboid body 2332 having a substantially square distalshape 2334. The cuboid body 2332 may include distal rounded corners 2336shaped to engage the recess 2310 when the drive gear 2302 is retractedinto the docking cap 2306. The drive gear 2302 may further include aproximal portion 2338 including a proximally tapering body 2340, whichenables easier initial insertion of the drive gear 2302 into the recess2310 and facilitates alignment of the drive gear 2302 with the dockingcap 2306.

FIG. 26 illustrates an alternative implementation of a docking system2600 including a drive gear 2602 engaged with a docking cap 2602.Similar to the drive gear 2302 and the docking cap 2306 as illustratedin FIG. 23E, the docking cap 2602 includes a recess 2610 shaped toreceive the drive gear 2602. Once received, the drive gear 2602 may berotated such that a corner 2616 a of the drive gear engages a wall 2612a of the recess 2610, thereby enabling transfer of torque applied to thedrive gear 2602 to the docking cap 2606. In contrast to the docking cap2306 of FIG. 23E, the docking cap 2606 defines a pair of cutouts 2650 a,2650 b extending into each of the wall 2612 a and an opposite wall 2612b, respectively. The cutouts 2650 a, 2650 b are arranged such thatinterference between the drive gear 2602 and the docking cap 2606 occursat only one point, thereby enabling self-alignment of the drive gear2602 relative to the docking cap 2606 by application of torque to thedrive gear 2602. Accordingly, in the implementation of FIG. 26, thecorner 2616 a functions as a torque feature of the drive gear 2602 thatengages a corresponding recess torque feature in the form of the portionof the wall 2612 a adjacent the cutout 2650 a.

FIGS. 27-29 illustrate another alternative implementation of a dockingsystem 2700 including a drive gear 2702 and a docking cap 2706 inaccordance with the present disclosure. As illustrated in FIGS. 27 and29, the docking cap 2706 defines a recess 2710 and further includesprotrusions 2750 a, 2750 b that extend laterally from the docking cap2706 into the recess 2710.

In contrast to the square-shaped drive gears 2302, 2602 illustrated inFIGS. 23-26, the drive gear 2702 of the docking system 2700 is formed tohave a star-shaped design. Referring to FIG. 28, which is an isometricview of the drive gear 2702, the drive gear 2702 includes an outer face2760 including multiple concave sections, such as concave section 2762.The concave section 2762 is shaped to receive the protrusions 2750 a,2750 b as the drive gear 2702 is rotated within the recess. The concavesection 2762 is connected to a substantially flat portion 2763 of theouter face 2760 by a transition portion 2764. The flat portion 2763 andthe transition portion 2764 are positioned relative to the concavesection 2762 such that when one of the protrusions 2750 a, 2750 b isreceived by the concave section 2762, further rotation of the drive gear2702 results in interference between the protrusion and the transitionportion 2764. Accordingly, the transition portion 2764 functions as atorque feature that transfers torque from the drive gear 2702 to acorresponding recess torque feature in the form of one of theprotrusions 2750 a, 2750 b of the docking cap 2706.

FIGS. 30A and 30B illustrate yet another implementation of a dockingsystem 3000 according to the present disclosure. As illustrated in FIG.30A, which is an isometric view of the docking system 3000, the dockingsystem 3000 includes a drive gear 3002 that is retractable into a recess3010 of a docking cap 3006. The drive gear 3002 may be shaped aspreviously described such that when retracted within a recess 3010 ofthe docking cap 3006, the drive gear 3002 may be rotated to engage thedocking cap 3006 such that torque applied to the drive gear 3002 by thetorque shaft 3004 is transferred to the docking cap 3006.

Referring back to FIGS. 23D and 23E, the recess 2310 of the previouslydescribed docking cap 2306 was defined by a substantially flat bottomsurface from which the walls defining the recess 2310 extended in asubstantially perpendicular direction. In contrast, the decking cap 3006includes proximally slanted surfaces 3050 a, 3050 b that extend alongthe depth of the recess 3010. One such slanted surface 3050 a is moreclearly visible in FIG. 30B, which is an isometric cross-sectional viewof the docking cap 3006. During operation, the slanted surfaces 3050 a,3050 b guide the drive gear 3002 to seat within the docking cap 3006 inresponse to both proximal pulling and rotation applied to the drive gear3002. Once seated, the drive gear 3002 may engage the docking cap 3006as previously described. For example, in certain implementations, acorner of the drive gear 3006 may interfere with a wall defining therecess 3010 or the drive gear 3006 may include concave surfaces adaptedto receive and engage protrusions extending into the recess 3010.

H. Expandable Sleeve for Leadless Pacemaker Delivery and Retrieval

The delivery and retrieval systems in accordance with this disclosuremay also include atraumatic by configurations that can be extended overthe leadless pacemaker and primary fixation mechanism when the leadlesspacemaker is being delivered into, or withdrawn from, the patient. Theatraumatic tip configurations can also be retracted from about theleadless pacemaker and primary fixation mechanism when the primaryfixation mechanism is caused to displace relative to the heart tissuesuch as when the primary fixation mechanism is in the form of a helixand is screwed into or out of the heart tissue at an implantation site.

FIG. 31 illustrates a system 3100 configured for delivery of a leadlesspacemaker 3102 into a patient and/or retrieval of the leadless pacemaker3102 from the patient. The system 3100 can include a guide cathetersheath 3111 including an atraumatic distal end 3104 in the form of asleeve 3104. Delivery system 3100 can also have a pacemaker introducersheath 3107 and a catheter shaft 3106. Catheter shaft 3106 includes atits proximal end a handle 3108, deflection knob 3110, and tether shuttle3112. Each of longitudinal bodies 3107, 3111, 3106 includes a flush port3114 a, 3114 b, 3114 c extending respectively therefrom. As can beunderstood from FIG. 31, the catheter shaft 3106 extends through theguide catheter sheath 111, which extends through the introducer sheath107. Each of the longitudinal bodies 3106, 3107, 3111 are displaceableproximal-distal relative to each other.

As discussed in greater detail below, the atraumatic sleeve 3104 may beformed of a shape-memory material that is sufficiently flexible to allowthe atraumatic sleeve 3104 to encompass the leadless pacemaker 3102 orto have a diameter that is smaller than a diameter of the leadlesspacemaker 3102 when not encompassing the leadless pacemaker 3102. Thedeflection knob 3110 can be used to deflect the catheter shaft 3106within the catheter sheath 3111 to steer and guide the catheter shaft3106 during implantation and/or removal of the leadless pacemaker 3102.The flush ports 3114 a, 3114 b, and 3114 c can be used to flush salineor other fluids through the catheter. The atraumatic sleeve 3104 formsthe distal most region of the catheter sheath 3111. The catheter sheath3111 can be advanced distally over the catheter shaft 3106 such that theatraumatic sleeve 3104 is caused to extend over the leadless pacemaker3102. Also, distal displacement of the catheter sheath 3111 relative tothe catheter shaft 3106 can be used to provide additional steering andsupport for the delivery catheter during implantation and to surroundthe pacemaker as it is introduced through a trocar or the introducersheath 3107 into the patient. The catheter sheath 3111 can be retractedproximally over the catheter shaft 3106 such that the atraumatic sleeve3104 is caused to retract from over the leadless pacemaker 3102, theshape-memory construction of the atraumatic sleeve 3104 being such thatatraumatic sleeve 3104 self-biases into a reduced diameter. In oneembodiment, the reduced diameter of the atraumatic sleeve 3104 is nogreater than the diameter of the leadless pacemaker 3102.

Alternatively, the sleeve 3104 may have a neutral shape it assumes orbiases into wherein its internal diameter is the same as the outerdiameter of the leadless pacemaker 3102 such that the sleeve 3104 canreadily slip over and off of the leadless pacemaker 3102 without thesleeve 3104 changing its internal diameter. However, on account of theflexibility and shape memory nature of the sleeve 3104, the sleeve 3104can be compressed for passage through the introducer 3107 and, oncethrough the introducer 3107, the shape memory nature of the sleeve 3104causes the sleeve 3104 to assume its neutral shape with its internaldiameter that is the same as the outer diameter of the leadlesspacemaker 3102.

FIG. 32A is a close-up view of a distal portion of a system 3200 andpacemaker 3202, and FIG. 32B is a diagrammatic longitudinal crosssection of the same components in the same condition. The pacemaker 3202of FIGS. 32A and 32B can include a helix 3203 for attachment of thepacemaker 3202 to tissue. In FIGS. 32A and 32B, the pacemaker 3202 isattached to a docking cap 3218 of the catheter shaft 3206. Theatraumatic sleeve 3204, along with the rest of the guide catheter sheath3211, is shown pulled back proximally along the catheter shaft 3206 toexpose the pacemaker 3202 and the helix 3203. Thus, when the guidecatheter sheath 3211 is pulled back proximally thereby causing itsatraumatic distal end region 3204 to pull back proximally, as shown inFIGS. 2A and 2B, the pacemaker 3202 is in an exposed, deliveryconfiguration such that the helix 3203 is exposed for screwing into orout of heart tissue at a implantation target site.

In FIGS. 32C and 32D, the guide catheter sheath 3211 is extendeddistally to cause the atraumatic sleeve 3204 to cover the catheter shaft3206, the pacemaker 3202, and the helix 3203 to protect patient tissuefrom the sharp edges of the helix 3203 during implantation. Thus, whenthe catheter sheath 3211 and its atraumatic distal end region 3204 inthe form of the sleeve 3204 are advanced distally to protect thepacemaker 3202 and the helix 3203, as shown in FIGS. 32C and 32D, thepacemaker 3202 and the helix 3203 are in a protected, advancementconfiguration.

FIG. 33A is a close-up view of the atraumatic distal end region 3204 ofthe sleeve 3304 of the catheter sheath of the delivery system. FIG. 33Aillustrates the sleeve 3304 in a contracted condition. The sleeve 3304extends between a trailing end 3302 and a leading end 3311 and includesa body 3305 that is longitudinally pleated so as to include a pluralityof generally rectangular segments 3310 extending from the trailing end3302 to the leading end 3311, the segments 3310 being connected to oneanother in a circumferential manner to define a lumen 3308 through thebody 3305. The body 3305 has a substantially star-shaped cross-section,with each segment 3310 being joined to adjacent segments along edges3312 a, 3312 b to define outer vertices 3314 a and inner vertices 3314 bof the star-shaped body 3305. As shown, the body 3305 includes six outervertices 3314 a and six inner vertices 3314 b, but it will be understoodthat the body 3305 may include multiple segments 3310 and that the term“star-shaped configuration” may refer to any configuration having threeor more outer vertices 3314 a and three or more inner vertices 3314 b.In its expanded condition, the sleeve 3304 may have a maximumcross-section “cs1,” measured from one outer vertex 3314 a to adiametrically opposed outer vertex 3314 a, that is from and includingapproximately 12 French to and including approximately 25 French.

The body 3305 may be formed of a shape-memory material that is heat-setinto the star-shaped configuration of FIG. 33A. In some examples, athermoplastic elastomer, such as polyether block amide (“PEBAX®”), witha durometer of approximately 25 to approximately 72 on scale D, may beused to form the body 3305. The segments 3310 may have a thickness ofabout 0.020″. The edges 3312 a, 3312 b may also have a thickness ofapproximately 0.020″ or less such that the vertices 3314 a, 3314 b areformed at predetermined positions to act as living hinges. The durometerof the polymer can be adjusted for either added flexibility or increasedaxial rigidity, depending on the application or desired performance.

FIG. 33B is a traverse cross-section of the sleeve 3304 in an expandedposition over the leadless pacemaker 3202. FIG. 330 is a side view ofthe sleeve 3304 in a contracted position. The body 3305 may be flexibleso that when the pacemaker 3202 is passed through the lumen 3308, thesegments 3310 are capable of being pushed radially outward so that thebody 3305 transitions from the contracted condition of FIG. 330 to anexpanded condition shown in FIG. 33B. In both the contracted conditionof FIG. 330 and expanded condition shown in FIGS. 33A and 33B, the body3305 may include a star configuration. However, in the expandedcondition shown in FIGS. 33A and 33B, the body 305 assumes a slightlymore tubular/rounded configuration than shown in FIG. 33C. In FIGS. 33A,33B, and 33C, the star configuration of the body 305 includes six outerpoints 3360 a-f and six inner points 3362 a-f. At each outer point 3360a-f, the star configuration of the body 3305 includes a pocket recess3364 a-f.

The pocket recesses 3364 a-f allow the sleeve 3304 to collapse andexpand to account for different size pacemakers with varying degrees oftissue overgrowth. During retrieval, the pacemakers can have unknownamounts of tissue growth on the pacer body. To accommodate thisvariation, the inner diameter of the inner points 3362 a-f can beadjusted to whatever size pacemaker is required, including any potentialtissue overgrowth, to achieve the desired fit. By making the sleeve 3304expandable to account for unknown amounts of tissue and/or differentsized pacemakers, the sleeve 3304 can help align the pacemaker axiallyand improve torque transmission with the walls of the sleeve 3304applying friction to deliver the pacemaker with the to pacemakerdelivery system 3100 (FIG. 31). During a leadless pacemaker retrievaloperation, the inner points 3362 a-f of the star configuration of thebody 3305 may also be used to score, scrape, or otherwise free thepacemaker from tissue overgrowth by rotating the sleeve 3304 around thepacemaker. Other constructions of the sleeve 3304 besides a star-shapemay also be used to score tissue overgrowth from the pacemaker.

FIGS. 34A and 34B illustrate a star configuration of the body 3305including four outer points, 3360 a-d, four inner points, 3362 a-d, andfour pocket recess 3364 a-d. FIG. 34A is a transverse cross section ofan embodiment of the pacemaker 3202 within the lumen 3308 of the sleeve3304. FIG. 346 is a &de view of a contracted sleeve 3304.

FIGS. 35A and 35B illustrate a star configuration of the body 3305including five outer points 3360 a-e, five inner points 3362 a-e, andfive pocket recess 3364 a-e. FIG. 35A is a transverse cross section ofan implementations of pacemaker 3202 within lumen 3308 of sleeve 3304.FIG. 35B is a side view of a contracted sleeve 3304.

In certain implementations, the body 3305 may include more or fewerinner and outer points and pocket recesses than illustrated. Moreover,the number of inner points 3362 and the outer diameter of the points3362 may be adjusted to create adequate clearance for varying amounts oftissue growth on the pacemaker 3202 and pacemakers having differentdiameters. In certain implementations, the body 3305 may be segmented ordiscontinuous about its circumferential extent. Conversely, the body maybe non-segmented or continuous about its circumferential extent.

FIGS. 36A and 36B are fluoroscopic images of a distal end of anatraumatic sleeve in accordance with this disclosure. As illustrated inFIG. 3H, a rectangular radiopaque marker 3380 at the distal end of theatraumatic sleeve may be used to determine under fluoroscopy thelocation of the atraumatic tip and, in particular, the location of theatraumatic tip with respect to the leadless pacemaker. For example, insome implementations, fluoroscopy may be implemented to determinewhether the distal tip of the atraumatic sleeve 3204 has past the helix3203 of the leadless pacemaker 3202 (as shown in FIG. 32D), such thatthe sharp edges of the helix 3203 are not exposed to surroundingsensitive tissue.

Certain prior leadless retrieval and delivery catheter systems used asleeve including ePTFE with a flat 90/10 Ptlr tip marker 1.27 mm×3.175mm placed in the wall 2 mm from the distal tip. In order to maintain alower catheter profile (i.e., a smaller French size), which affects thesafety and comfort of the procedure, a full round marker band may not beused in implementations of the current disclosure. However, a radiopaquefeature around the entire distal tip of sleeve 3304 would improvevisibility for a user, aiding in determining whether the distal tip ofthe atraumatic sleeve 3304 is past the helix 3203 of the pacemaker 3202,such that the sharp edges of helix 3203 are not exposed to surroundingsensitive tissue.

This disclosure provides for apparatuses and methods that could beemployed to maintain the flexibility of sleeve 3304, such that sleeve3304 repeatedly and reliably expands and compresses during a pacemakerretrieval or delivery procedure, while increasing the radiopacity of theatraumatic sleeve 3304, thereby improving safety of such procedures.

FIG. 36B illustrates the atraumatic sleeve 3304 in which pad printingradiopaque ink 3382 a, 3382 b has been applied the sleeve 3304. Inalternative implementations, radiopaque ink can be placed in interruptedspots in specific locations on the sleeve 3304. In certainimplementations, radiopaque medical ink, such as Class VI Medical gradeink, may be used in printing wherein tungsten or other high radiopaquemetals are loaded in medical grade ink and printed onto the surface ofthe sleeve 3304 by a suitable printing technique, such as, for example,engraving, mono-type, offset, cliché transfer, ink-jet or gliceéprinting. In one embodiment, an ink composition for radiopaque markerfor a PEBAX® surface includes a suitable polymeric binder that adhereswell to a PEBAX® surface, a biocompatible dye or pigment, a radiopaquematerial and a solvent that dissolves the polymeric binder. In addition,the ink composition may contain inorganic white solid materials such astitanium dioxide (to adjust ink shade) and a viscosity modifier.

Another method of providing a radiopaque marker could be to plate thesleeve 3304 at the distal tip with a radiopaque material that would beable to expand and collapse with the sleeve, without detrimentallyincreasing the diameter of the sleeve 3304 and without compromising theflexibility and expandability of the system. Providing a flexibleradiopaque marker around the entire distal tip of the sleeve 3304 alsoadvantageously improves visibility of the sleeve 3304 compared to priorart marker squares. In certain implementations, the radiopaque markermay be applied from a solution of dissolved metal. The attachmentmechanism can occur either using an electrical current to drive theattachment reaction, or more preferably by utilizing an autocatalyticchemical reaction requiring no electrical motive force, i.e., anelectroless plating reaction. A significant advantage of the electrolessplating process is the ability to produce deposits with uniformthickness on parts with complex geometries and shapes. Examples ofelectroless plating processes and compositions that may be used inaccordance with the present invention are disclosed in U.S. Pub. No.2016/0121007 and U.S. Pat. Nos. 3,123,484; 3,148,072, 3,338,726,3,719,508, 3,745,039, 3,754,939, 3,915,717, 4,152,164, 6,143,059,6,281,157, 6,524,642, 7,846,503, and 9,462,699, each of which isincorporated herein by reference. In certain implementations, radiopaquematerial of radiopaque marker 370 may include tungsten, platinum, gold,or etc. that may be plated to sleeve 3304.

In certain implementations, at least the distal tip of sleeve 3304 mayinclude a dual-wall construction including a woven wire band residingbetween a PEBAX® inner wall and PEBAX® outer wall, wherein the wovenwire includes radiopaque wires braided with non-radiopaque wires. In oneembodiment, the wires may have a diameter range of approximately 0.003inch and approximately 0.01 inch. In accordance with this embodiment,the radiopaque braid would be able to expand and collapse with thesleeve, without detrimentally increasing the diameter of the sleeve 3304and without compromising the flexibility and expandability of thesystem, while providing a flexible radiopaque marker around the entiredistal tip of sleeve 3304. The mechanical properties of the radiopaquewires are selected to match the mechanical properties of thenon-radiopaque wires, in order to increase the durability andconsistence of the mesh, while providing for a self-expanding orself-contracting radiopaque marker band. The non-radiopaque wires caninclude superelastic material. In certain implementations, at least someof the radiopaque wires may include radiopaque nitinol (a ternary ahoyconsisting of a blend of nickel, titanium, and platinum) to provide fora more superelastic marker material. U.S. Pat. No. 9,320,590,incorporated herein by reference, discloses radiopaque wire andnon-radiopaque wire components of woven wire bands that may be used inaccordance with the implementations of the invention. U.S. Pub. No.2016/0121007, incorporated herein by reference, describes a method ofplating a braided wire that may be used in accordance withimplementations of the invention to join the wires to each other atpoints of contact that torsionally stiffens the braid, while stillpermitting flexibility in the braid.

In certain implementations, the dual-wall construction may be includedthroughout the sleeve 3304, in order to provide reinforcement. The wirereinforcement may include at least one of longitudinally extendingwires, radially extending wire rings, or a lattice of longitudinallyextending wires and radially extending wire rings. The stiffening wiresmay be in the form of a plurality of longitudinally extending wiresevenly radially dispersed in the space between the inner and outerwalls. Alternatively, the stiffening wires may be in the form of aplurality of radial rings evenly longitudinally dispersed in the spacebetween the inner and outer walls. In yet another alternative, theplurality of longitudinally extending wires and plurality of radialrings may be combined to form a wire mesh or lattice between the innerand outer walls. Regardless of how the stiffening wires are arrangedbetween the inner and outer walls, the stiffening wires increase thecolumn strength of the sleeve.

In some implementations, the length of the sleeve 3304 may have a rangeof approximately 2 inches to approximately 3 inch with a preferredlength range of approximately 2.5 inches depending on the length of theleadless pacemaker to be received in the sleeve 3304. In one embodiment,the thermoplastic elastomer of the sleeve 3304 may include: a polyetherblock amide (“PEBAX®”), polyethylene terephthalate (“PET”), polyethylene(“PE”), nylon, urethane, polyester, or a blend of any of theaforementioned where appropriate.

In certain implementations, the sleeve 3304 is coated with ahydrophilic, drug, parylene or silicone base coating to inhibit orprevent thrombus during the procedure.

In certain implementations, the sleeve 3304 is manufactured by a moldingor extrusion process and coupled to the rest of the catheter sheath 3311via a method 3700 outlined in flow chart of FIG. 37. In accordance withone implementation of the method 3700, a first step 3702 includesmanufacturing a PEBAX® star-shaped sleeve using an injected moldingprocess. At step 384, a radiopaque maker is added to the sleeve using aradiopaque ink. In certain implementations, the radiopaque marker isapplied all the way around the sleeve (such as by applying a completeband or interrupted spots in specific locations) or by plating thesleeve at the tip with a radiopaque material that is able to expand andcollapse with the sleeve, as described in more detail above. At step3704, the sleeve is then thermally bonded to the guide sheath of thedelivery system.

FIG. 38 is a flow chart of an alternative method 3800 of manufacturing asleeve in accordance with this disclosure in which the sleeve is formed,in part using a heat flow extrusion process. At step 3802, a PEBAX®extruded tube is obtained with an oval cross-section of 1.27×0.69 mmO.D. At step 3804, the extruded tube are heat set or cross-linked byirradiation (e.g. gamma radiation or electron beam radiation) to sustainthe star configuration. In certain implementations, the composite tubefurther includes a coil, braid, or stent reinforcement.

At step 3806, a radiopaque maker is added to the sleeve in certainimplementations, the radiopaque marker is applied all the way around thesleeve (such as by applying a complete band or interrupted spots inspecific locations) or by plating the sleeve at the tip with aradiopaque material that is able to expand and collapse with the sleeve,as described in more detail above. At step 3808 a tapered section isformed on the sleeve by again heat setting the tube. At step 3812, thetaper section of the sleeve is then thermally bonded to the guide sheathof the delivery system.

FIG. 39 is a flow chart of another method 3900 of manufacturing ofmanufacturing a sleeve in accordance with this disclosure and, inparticular, forming a PEBAX® star-shaped sleeve is manufactured througha multistage blow molding process. According to the method 3900, at step3902 a piece of extrusion is used to form a parison using heat,pressure, and tension. At step 3904, the parison is fed into amulti-piece mold system. The molds of the multi-piece mold system mayconsist of cavities designed to the exterior dimensions of the desiredpart. At step 3906, using heat and pressure, the parison is blown in themold cavities to form a subassembly. In certain implementations,pressure in the range of 300 psi to 500 psi is used. In certainimplementations, a pressure of 290 psi is used. In certainimplementations, the subassembly is heat-set using a temperature in therange of 85-200° C. In certain implementations, the subassembly isheat-set using a temperature of approximately 149° C. or 300° F. Theblow molding may consist of multiple cycles to form specific features,i.e. atraumatic tips or cone neck geometry. In certain implementations,the subassembly is post processed at step 3908, i.e. tipping, final cutto length, etc.

FIG. 40 is a flow chart of another method 4000 of manufacturing ofmanufacturing a sleeve in accordance with this disclosure and, inparticular, forming a PEBAX® star-shaped sleeve through a multistageblow molding process. At step 4002, a piece of extrusion is used to forma parison using heat, pressure, and tension. At step 4004, the parisonis fed into a multi piece mold system. The molds may consist of cavitiesdesigned to the exterior dimensions of the desired part. Using heat andpressure, at step 4006, the parison is blown in the mold cavities toform a subassembly.

In certain implementations, the blow molding process yields asymmetrical assembly. At step 4008, the symmetrical assembly is cutcentrally to form two subassemblies. At step 4010, the subassemblies arepost processed to form an atraumatic tip.

After the delivery system is inserted through the introducer sheath intothe patient, the sheath can be advanced distally over the leadlesspacemaker. Advancing the sleeve distally over the pacemaker causes thepocket recesses of the star configuration to expand, thereby increasingthe diameter of the sleeve so that it can slide over and cover thepacemaker and fixation helix.

During initial insertion of the delivery system into a patient, aphysician can gain access to the patient's venous system with anintroducer sheath using the Seldinger technique (not shown). Thedelivery system, including the leadless pacemaker, catheter sheath andcatheter shaft, can then be advanced through the introducer sheath intothe patient's venous system to facilitate delivery of the pacemaker intothe heart. Reducing the diameter of the pacemaker, the delivery system,and thus the introducer sheath, provides for easier and less intrusiveaccess to a patient's venous system.

FIG. 41 is an isometric view of an alternative sleeve 4104 that may beused with the catheter sheath of the delivery system. FIG. 41illustrates the sleeve 4104 in a contracted condition. The sleeve 4104extends between a trailing end 4102 and a leading end 4111 and includesa body 4105.

The body 4105 includes a leading body portion 4107, a trailing bodyportion 4108, and an intermediate body portion 4109 extending betweenthe leading body portion 4107 and the trailing body portion 4108. Theintermediate body portion 4109 may include longitudinal pleats or foldssuch that the intermediate body portion 4109 includes a star-shaped orother cross-section in accordance with this disclosure. For example, theintermediate body portion 4109 may have a cross-section similar to anyof the implementations illustrated FIGS. 33A-35B.

FIGS. 42A is a longitudinal side-view of the alternative sleeve 4104 andFIGS. 42B-42D are cross-sections taken along A-A, B-B, and C-C,respectively. More specifically, cross-section A-A is a cross-sectionalview of the intermediate body portion 4108 directed in the proximaldirection, cross-sectional view B-B is a cross-sectional view of thetrailing body portion 4108 directed in the proximal direction, andcross-sectional view C-C is a cross-sectional view of the leading bodyportion 4107 directed in the distal direction. In certainimplementations, the leading body portion 4107 may extend approximately0.600 inches, the intermediate body portion 4109 may extendapproximately 1.330 inches, and the trailing body portion 4108 mayextend approximately 0.450 inches with a tapered transitional portion4110 extending between the intermediate body portion 4109 and thetrailing body portion 4108.

As shown in FIGS. 42A-42D, the leading body portion 4107 may have definea first internal diameter 4120, the intermediate body portion 4108 mayinclude points 4122 or similar features that define a minimum innerdiameter 4126 and a maximum outer diameter 4128, and the trailing bodyportion 4108 may define a second internal diameter 4130. In certainimplementations, various diameters defined by the portions of thealternative sleeve 4104 may reduce toward the trailing end portion 4106.For example, the first internal diameter 4120 may be greater than orequal to the maximum outer diameter 4128 and the minimum inner diameter4126 may be greater than the second internal diameter 4130. For example,in certain implementations, the first internal diameter 4120 may beapproximately 0.300 inches, the maximum outer diameter 4128 may beapproximately 0.290 inches, the minimum inner diameter may beapproximately 0.200 inches and the second internal diameter 4130 may beapproximately 0.184 inches,

As can be understood from FIGS. 32A-42D, sleeves according to thisdisclosure may have a woven expandable configuration that self-biases toa reduced diameter that is at least as small as the diameter of aleadless pacemaker being delivered or retrieved and is sufficientlyreadily expandable by simply distally displacing the sleeve against theleadless pacemaker such that the sleeve expands about and envelopesleadless pacemaker. Thus, during initial implantation of the pacemakerthrough an introducer sheath into the patient, the sleeve can bepositioned just proximal to the pacemaker, as illustrated in FIGS.32A-32B, the diameter of the sleeve self-biasing to its minimum diameterso as to have a cross sectional diameter close to or equal to the samediameter as the pacemaker. This allows a smaller diameter introducersheath to be used than would normally be necessary, since those deliverysystems must incorporate a larger introducer sheath to avow passage of afull sized sleeve. After the delivery system is inserted through theintroducer sheath into the patient, the sheath can be advanced distallyover the leadless pacemaker. Advancing the sleeve distally over thepacemaker causes the braided or woven expandable configuration of thesleeve to expand sufficiently with respect to its diameter that thesleeve can slide over and cover the pacemaker and fixation helix, asillustrated in FIGS. 2C-2D, thereby preventing the helix from contactingpatient tissue.

It should be noted that while the sleeve is shown in FIGS. 32B and 32Das having a neutral configuration with an internal diameter that is lessthan the outer diameter of the leadless pacemaker, thereby requiring thesleeve to expand as it is distally displaced over the leadless pacemakerfor the leadless pacemaker to be received in the internal volume of thesleeve, in other implementations, the sleeve has a neutral configurationwith an internal diameter that is the same as the outer diameter of theleadless pacemaker. More specifically, the sleeve may have a neutralshape it assumes or biases into wherein its internal diameter is thesame as the outer diameter of the leadless pacemaker such that thesleeve can readily slip over and off of the leadless pacemaker withoutthe sleeve changing its internal diameter. However, on account of theflexibility and shape memory nature of the sleeve, the sleeve can becompressed for passage through the introducer and, once through theintroducer, the shape memory nature of the sleeve causes the sleeve toassume its neutral shape with its internal diameter that is the same asthe outer diameter of the leadless pacemaker.

Any of the above mentioned implementations may also include, withoutlimitation, electronic indicators on the system (e.g., LEDS or screens)or on adjunct support-screens to communicate status. Finally, the abovementioned implementations may also include shaft position indicatorsvia, for example, detents located on the shaft of the deflectablecatheter and complementary features for interacting on the detents, thecomplementary features being located on the guide catheter or even thelocking hub. Of course the opposite arrangement is also possible. Theposition indicator aspects can be used to notify the user of the extentto which the protective sleeve covers the leadless pacemaker.

As for additional details pertinent to the present invention, materialsand manufacturing techniques may be employed as within the level ofthose with skill in the relevant art. The same may hold true withrespect to method-based aspects of the invention in terms of additionalacts commonly or logically employed. Also, it is contemplated that anyoptional feature of the inventive variations described may be set forthand claimed independently, or in combination with any one or more of thefeatures described herein. Likewise, reference to a singular item,includes the possibility that there are plural of the same itemspresent. More specifically, as used herein and in the appended claims,the singular forms “a” “and,” “said,” and “the” include plural referentsunless the context clearly dictates otherwise. It is further noted thatthe claims may be drafted to exclude any optional element. As such, thisstatement is intended to serve as antecedent basis for use of suchexclusive terminology as “solely,” “only” and the like in connectionwith the recitation of claim elements, or use of a “negative”limitation. Unless defined otherwise herein, all technical andscientific terms used herein have the same meaning as commonlyunderstood by one of ordinary skill in the art to which this inventionbelongs. The breadth of the present invention is not to be limited bythe subject specification, but rather only by the plain meaning of theclaim terms employed.

What is claimed is:
 1. A system for retrieving an implantable medicaldevice from within a patient, the system comprising: a catheter shaft; atorque shaft disposed within the catheter shaft; a handle comprising afirst handle portion coupled to the catheter shaft and a second handleportion coupled to the torque shaft; a drive gear coupled to a distalend of the torque shaft and comprising a drive gear torque feature, thedrive gear rotatable by rotating the torque shaft; and a docking caprotatably coupled to a distal end of the catheter shaft, the docking capdefining a recess for at least partially receiving the drive gear, thedocking cap further comprising a recess torque feature disposed withinthe recess, wherein, when received by the docking cap, the drive gear isrotatable in a first direction into an engaged position in which thedrive gear torque feature engages the recess torque feature such thatfurther rotation of the drive gear rotates the docking cap in the firstdirection.
 2. The system of claim 1, wherein the drive gear comprises adistal portion comprising a cuboid body having a substantially squareshape.
 3. The system of claim 2, wherein the cuboid body includes distalrounded corners.
 4. The system of claim 2, wherein: the square distalface defines a diagonal between a pair of opposing corners of the squaredistal face; the recess is defined by a pair of first opposing walls anda pair of second opposing walls, the first opposing walls being longerthan the diagonal and the second opposing walls being shorter than thediagonal; the recess torque feature is one or both of the first opposingwalls; and the drive gear torque feature is one or both of the opposingcorners of the square distal face.
 5. The system of claim 1, wherein thedocking cap further defines a cutout in one of the first opposing walls,the cutout shaped to receive one of the opposing corners of the drivegear when the drive gear is in the engaged position.
 6. The system ofclaim 1, wherein the drive gear comprises a proximal portion comprisinga proximally tapering body.
 7. The system of claim 1, wherein thedocking cap comprises a protrusion extending laterally into the recess,the recess torque feature being the protrusion.
 8. The system of claim7, wherein the drive gear comprises an outer face comprising a concaveportion shaped to receive the protrusion during rotation of the drivegear in the first direction, a substantially flat portion, and atransition portion coupling the concave portion to the substantiallyflat portion, the drive gear torque feature being the transitionportion,
 9. The system of claim 1, wherein the docking cap comprises aproximally slanted surface extending into the recess, the proximallyslanted surface shaped to guide the drive gear into the engaged positionin response to rotation of the drive gear in the first direction. 10.The system of claim 1, wherein, when in the engaged position, rotationof the drive gear in a second direction opposite the first directiondisengages the drive gear torque feature from the recess torque feature.11. A system for retrieving an implantable medical device from within apatient, the system comprising: a drive gear; and a docking cap shapedto receive a proximal end of the implantable medical device, wherein thedrive gear is at least partially retractable within the docking cap and,when at least partially retracted within the docking cap, rotation ofthe drive gear in a first direction causes interference between thedrive gear and the docking cap such that further rotation of the drivegear in the first direction rotates each of the drive gear and thedocking cap.
 12. The system of claim 11, wherein the drive gearcomprises a rounded distal corner and the docking cap comprises aninternal wall partially defining a recess within the docking cap, theinterference being between the rounded distal corner and the internalwall.
 13. The system of claim 11, wherein the docking cap defines arecess and comprises a protrusion extending laterally into the recess,the drive gear comprises an outer face comprising a concave portionshaped to receive the protrusion during rotation of the drive gear inthe first direction, a substantially flat portion, and a transitionportion coupling the concave portion to the substantially flat portion,and the interference is between the transition portion and theprotrusion.
 14. The system of claim 11, wherein the drive gearinterferes with the docking cap at a plurality of locations.
 15. Thesystem of claim 11, wherein the drive gear comprises a distal portioncomprising a cuboid body having a substantially square distal face, thecuboid body including distal rounded corners.
 16. The system of claim11, wherein the drive gear comprises a proximal portion comprising aproximally tapering body.
 17. A system for delivering and retrieving animplantable medical device from within a patient, the system comprising:a catheter shaft; a torque shaft disposed within the catheter shaft; ahandle comprising a first handle portion coupled to the catheter shaftand a second handle portion coupled to the torque shaft; a drive gearcoupled to a distal end of the torque shaft, the drive gear comprising adistal portion comprising a cuboid body having a substantially squaredistal face and rounded distal corners, the square distal face defininga diagonal between opposing corners of the square distal face; and adocking cap rotatably coupled to a distal end of the catheter shaft, thedocking cap comprising; a pair of first opposing internal walls that areeach longer than the diagonal; and a pair of second opposing internalwalls that are each shorter than the diagonal, the pair of firstinternal opposing walls and the pair of second opposing internal wallsdefining a recess for at least partially receiving the drive gear. 18.The system of claim 17, wherein, when received within the recess, thedrive gear is rotatable in a first direction to engage at least one ofthe opposing corners with a respective one of the pair of first opposinginternal walls such that, once engaged, rotation of the drive gearrotates the docking cap.
 19. The system of claim 18, wherein, when theat least one of the opposing corners is engaged with the respective oneof the pair of first opposing internal walls, rotation of the drive gearin a second direction opposite the first direction disengages the atleast one of the opposing corners from the respective one of the pair offirst opposing internal walls.
 20. The system of claim 17, wherein thedrive gear further comprises a proximal portion coupled to the distalportion, the proximal portion comprising a proximally tapering body.